[cleanup] codebase cleanup

17 files changed, 2761 insertions, 677 deletions

diff --git a/3rdparty/stb_ds/LICENSE b/3rdparty/stb_ds/LICENSE
new file mode 100644
index 0000000..a77ae91
--- /dev/null
+++ b/3rdparty/stb_ds/LICENSE
@@ -0,0 +1,37 @@
+This software is available under 2 licenses -- choose whichever you prefer.
+------------------------------------------------------------------------------
+ALTERNATIVE A - MIT License
+Copyright (c) 2017 Sean Barrett
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+------------------------------------------------------------------------------
+ALTERNATIVE B - Public Domain (www.unlicense.org)
+This is free and unencumbered software released into the public domain.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+software, either in source code form or as a compiled binary, for any purpose,
+commercial or non-commercial, and by any means.
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and to
+the detriment of our heirs and successors. We intend this dedication to be an
+overt act of relinquishment in perpetuity of all present and future rights to
+this software under copyright law.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/3rdparty/stb_ds/stb_ds.h b/3rdparty/stb_ds/stb_ds.h
new file mode 100644
index 0000000..e84c82d
--- /dev/null
+++ b/3rdparty/stb_ds/stb_ds.h
@@ -0,0 +1,1895 @@
+/* stb_ds.h - v0.67 - public domain data structures - Sean Barrett 2019
+
+   This is a single-header-file library that provides easy-to-use
+   dynamic arrays and hash tables for C (also works in C++).
+
+   For a gentle introduction:
+      http://nothings.org/stb_ds
+
+   To use this library, do this in *one* C or C++ file:
+      #define STB_DS_IMPLEMENTATION
+      #include "stb_ds.h"
+
+TABLE OF CONTENTS
+
+  Table of Contents
+  Compile-time options
+  License
+  Documentation
+  Notes
+  Notes - Dynamic arrays
+  Notes - Hash maps
+  Credits
+
+COMPILE-TIME OPTIONS
+
+  #define STBDS_NO_SHORT_NAMES
+
+     This flag needs to be set globally.
+
+     By default stb_ds exposes shorter function names that are not qualified
+     with the "stbds_" prefix. If these names conflict with the names in your
+     code, define this flag.
+
+  #define STBDS_SIPHASH_2_4
+
+     This flag only needs to be set in the file containing #define STB_DS_IMPLEMENTATION.
+
+     By default stb_ds.h hashes using a weaker variant of SipHash and a custom hash for
+     4- and 8-byte keys. On 64-bit platforms, you can define the above flag to force
+     stb_ds.h to use specification-compliant SipHash-2-4 for all keys. Doing so makes
+     hash table insertion about 20% slower on 4- and 8-byte keys, 5% slower on
+     64-byte keys, and 10% slower on 256-byte keys on my test computer.
+
+  #define STBDS_REALLOC(context,ptr,size) better_realloc
+  #define STBDS_FREE(context,ptr)         better_free
+
+     These defines only need to be set in the file containing #define STB_DS_IMPLEMENTATION.
+
+     By default stb_ds uses stdlib realloc() and free() for memory management. You can
+     substitute your own functions instead by defining these symbols. You must either
+     define both, or neither. Note that at the moment, 'context' will always be NULL.
+     @TODO add an array/hash initialization function that takes a memory context pointer.
+
+  #define STBDS_UNIT_TESTS
+
+     Defines a function stbds_unit_tests() that checks the functioning of the data structures.
+
+  Note that on older versions of gcc (e.g. 5.x.x) you may need to build with '-std=c++0x'
+     (or equivalentally '-std=c++11') when using anonymous structures as seen on the web
+     page or in STBDS_UNIT_TESTS.
+
+LICENSE
+
+  Placed in the public domain and also MIT licensed.
+  See end of file for detailed license information.
+
+DOCUMENTATION
+
+  Dynamic Arrays
+
+    Non-function interface:
+
+      Declare an empty dynamic array of type T
+        T* foo = NULL;
+
+      Access the i'th item of a dynamic array 'foo' of type T, T* foo:
+        foo[i]
+
+    Functions (actually macros)
+
+      arrfree:
+        void arrfree(T*);
+          Frees the array.
+
+      arrlen:
+        ptrdiff_t arrlen(T*);
+          Returns the number of elements in the array.
+
+      arrlenu:
+        size_t arrlenu(T*);
+          Returns the number of elements in the array as an unsigned type.
+
+      arrpop:
+        T arrpop(T* a)
+          Removes the final element of the array and returns it.
+
+      arrput:
+        T arrput(T* a, T b);
+          Appends the item b to the end of array a. Returns b.
+
+      arrins:
+        T arrins(T* a, int p, T b);
+          Inserts the item b into the middle of array a, into a[p],
+          moving the rest of the array over. Returns b.
+
+      arrinsn:
+        void arrinsn(T* a, int p, int n);
+          Inserts n uninitialized items into array a starting at a[p],
+          moving the rest of the array over.
+
+      arraddnptr:
+        T* arraddnptr(T* a, int n)
+          Appends n uninitialized items onto array at the end.
+          Returns a pointer to the first uninitialized item added.
+
+      arraddnindex:
+        size_t arraddnindex(T* a, int n)
+          Appends n uninitialized items onto array at the end.
+          Returns the index of the first uninitialized item added.
+
+      arrdel:
+        void arrdel(T* a, int p);
+          Deletes the element at a[p], moving the rest of the array over.
+
+      arrdeln:
+        void arrdeln(T* a, int p, int n);
+          Deletes n elements starting at a[p], moving the rest of the array over.
+
+      arrdelswap:
+        void arrdelswap(T* a, int p);
+          Deletes the element at a[p], replacing it with the element from
+          the end of the array. O(1) performance.
+
+      arrsetlen:
+        void arrsetlen(T* a, int n);
+          Changes the length of the array to n. Allocates uninitialized
+          slots at the end if necessary.
+
+      arrsetcap:
+        size_t arrsetcap(T* a, int n);
+          Sets the length of allocated storage to at least n. It will not
+          change the length of the array.
+
+      arrcap:
+        size_t arrcap(T* a);
+          Returns the number of total elements the array can contain without
+          needing to be reallocated.
+
+  Hash maps & String hash maps
+
+    Given T is a structure type: struct { TK key; TV value; }. Note that some
+    functions do not require TV value and can have other fields. For string
+    hash maps, TK must be 'char *'.
+
+    Special interface:
+
+      stbds_rand_seed:
+        void stbds_rand_seed(size_t seed);
+          For security against adversarially chosen data, you should seed the
+          library with a strong random number. Or at least seed it with time().
+
+      stbds_hash_string:
+        size_t stbds_hash_string(char *str, size_t seed);
+          Returns a hash value for a string.
+
+      stbds_hash_bytes:
+        size_t stbds_hash_bytes(void *p, size_t len, size_t seed);
+          These functions hash an arbitrary number of bytes. The function
+          uses a custom hash for 4- and 8-byte data, and a weakened version
+          of SipHash for everything else. On 64-bit platforms you can get
+          specification-compliant SipHash-2-4 on all data by defining
+          STBDS_SIPHASH_2_4, at a significant cost in speed.
+
+    Non-function interface:
+
+      Declare an empty hash map of type T
+        T* foo = NULL;
+
+      Access the i'th entry in a hash table T* foo:
+        foo[i]
+
+    Function interface (actually macros):
+
+      hmfree
+      shfree
+        void hmfree(T*);
+        void shfree(T*);
+          Frees the hashmap and sets the pointer to NULL.
+
+      hmlen
+      shlen
+        ptrdiff_t hmlen(T*)
+        ptrdiff_t shlen(T*)
+          Returns the number of elements in the hashmap.
+
+      hmlenu
+      shlenu
+        size_t hmlenu(T*)
+        size_t shlenu(T*)
+          Returns the number of elements in the hashmap.
+
+      hmgeti
+      shgeti
+      hmgeti_ts
+        ptrdiff_t hmgeti(T*, TK key)
+        ptrdiff_t shgeti(T*, char* key)
+        ptrdiff_t hmgeti_ts(T*, TK key, ptrdiff_t tempvar)
+          Returns the index in the hashmap which has the key 'key', or -1
+          if the key is not present.
+
+      hmget
+      hmget_ts
+      shget
+        TV hmget(T*, TK key)
+        TV shget(T*, char* key)
+        TV hmget_ts(T*, TK key, ptrdiff_t tempvar)
+          Returns the value corresponding to 'key' in the hashmap.
+          The structure must have a 'value' field
+
+      hmgets
+      shgets
+        T hmgets(T*, TK key)
+        T shgets(T*, char* key)
+          Returns the structure corresponding to 'key' in the hashmap.
+
+      hmgetp
+      shgetp
+      hmgetp_ts
+      hmgetp_null
+      shgetp_null
+        T* hmgetp(T*, TK key)
+        T* shgetp(T*, char* key)
+        T* hmgetp_ts(T*, TK key, ptrdiff_t tempvar)
+        T* hmgetp_null(T*, TK key)
+        T* shgetp_null(T*, char *key)
+          Returns a pointer to the structure corresponding to 'key' in
+          the hashmap. Functions ending in "_null" return NULL if the key
+          is not present in the hashmap; the others return a pointer to a
+          structure holding the default value (but not the searched-for key).
+
+      hmdefault
+      shdefault
+        TV hmdefault(T*, TV value)
+        TV shdefault(T*, TV value)
+          Sets the default value for the hashmap, the value which will be
+          returned by hmget/shget if the key is not present.
+
+      hmdefaults
+      shdefaults
+        TV hmdefaults(T*, T item)
+        TV shdefaults(T*, T item)
+          Sets the default struct for the hashmap, the contents which will be
+          returned by hmgets/shgets if the key is not present.
+
+      hmput
+      shput
+        TV hmput(T*, TK key, TV value)
+        TV shput(T*, char* key, TV value)
+          Inserts a <key,value> pair into the hashmap. If the key is already
+          present in the hashmap, updates its value.
+
+      hmputs
+      shputs
+        T hmputs(T*, T item)
+        T shputs(T*, T item)
+          Inserts a struct with T.key into the hashmap. If the struct is already
+          present in the hashmap, updates it.
+
+      hmdel
+      shdel
+        int hmdel(T*, TK key)
+        int shdel(T*, char* key)
+          If 'key' is in the hashmap, deletes its entry and returns 1.
+          Otherwise returns 0.
+
+    Function interface (actually macros) for strings only:
+
+      sh_new_strdup
+        void sh_new_strdup(T*);
+          Overwrites the existing pointer with a newly allocated
+          string hashmap which will automatically allocate and free
+          each string key using realloc/free
+
+      sh_new_arena
+        void sh_new_arena(T*);
+          Overwrites the existing pointer with a newly allocated
+          string hashmap which will automatically allocate each string
+          key to a string arena. Every string key ever used by this
+          hash table remains in the arena until the arena is freed.
+          Additionally, any key which is deleted and reinserted will
+          be allocated multiple times in the string arena.
+
+NOTES
+
+  * These data structures are realloc'd when they grow, and the macro
+    "functions" write to the provided pointer. This means: (a) the pointer
+    must be an lvalue, and (b) the pointer to the data structure is not
+    stable, and you must maintain it the same as you would a realloc'd
+    pointer. For example, if you pass a pointer to a dynamic array to a
+    function which updates it, the function must return back the new
+    pointer to the caller. This is the price of trying to do this in C.
+
+  * The following are the only functions that are thread-safe on a single data
+    structure, i.e. can be run in multiple threads simultaneously on the same
+    data structure
+        hmlen        shlen
+        hmlenu       shlenu
+        hmget_ts     shget_ts
+        hmgeti_ts    shgeti_ts
+        hmgets_ts    shgets_ts
+
+  * You iterate over the contents of a dynamic array and a hashmap in exactly
+    the same way, using arrlen/hmlen/shlen:
+
+      for (i=0; i < arrlen(foo); ++i)
+         ... foo[i] ...
+
+  * All operations except arrins/arrdel are O(1) amortized, but individual
+    operations can be slow, so these data structures may not be suitable
+    for real time use. Dynamic arrays double in capacity as needed, so
+    elements are copied an average of once. Hash tables double/halve
+    their size as needed, with appropriate hysteresis to maintain O(1)
+    performance.
+
+NOTES - DYNAMIC ARRAY
+
+  * If you know how long a dynamic array is going to be in advance, you can avoid
+    extra memory allocations by using arrsetlen to allocate it to that length in
+    advance and use foo[n] while filling it out, or arrsetcap to allocate the memory
+    for that length and use arrput/arrpush as normal.
+
+  * Unlike some other versions of the dynamic array, this version should
+    be safe to use with strict-aliasing optimizations.
+
+NOTES - HASH MAP
+
+  * For compilers other than GCC and clang (e.g. Visual Studio), for hmput/hmget/hmdel
+    and variants, the key must be an lvalue (so the macro can take the address of it).
+    Extensions are used that eliminate this requirement if you're using C99 and later
+    in GCC or clang, or if you're using C++ in GCC. But note that this can make your
+    code less portable.
+
+  * To test for presence of a key in a hashmap, just do 'hmgeti(foo,key) >= 0'.
+
+  * The iteration order of your data in the hashmap is determined solely by the
+    order of insertions and deletions. In particular, if you never delete, new
+    keys are always added at the end of the array. This will be consistent
+    across all platforms and versions of the library. However, you should not
+    attempt to serialize the internal hash table, as the hash is not consistent
+    between different platforms, and may change with future versions of the library.
+
+  * Use sh_new_arena() for string hashmaps that you never delete from. Initialize
+    with NULL if you're managing the memory for your strings, or your strings are
+    never freed (at least until the hashmap is freed). Otherwise, use sh_new_strdup().
+    @TODO: make an arena variant that garbage collects the strings with a trivial
+    copy collector into a new arena whenever the table shrinks / rebuilds. Since
+    current arena recommendation is to only use arena if it never deletes, then
+    this can just replace current arena implementation.
+
+  * If adversarial input is a serious concern and you're on a 64-bit platform,
+    enable STBDS_SIPHASH_2_4 (see the 'Compile-time options' section), and pass
+    a strong random number to stbds_rand_seed.
+
+  * The default value for the hash table is stored in foo[-1], so if you
+    use code like 'hmget(T,k)->value = 5' you can accidentally overwrite
+    the value stored by hmdefault if 'k' is not present.
+
+CREDITS
+
+  Sean Barrett -- library, idea for dynamic array API/implementation
+  Per Vognsen  -- idea for hash table API/implementation
+  Rafael Sachetto -- arrpop()
+  github:HeroicKatora -- arraddn() reworking
+
+  Bugfixes:
+    Andy Durdin
+    Shane Liesegang
+    Vinh Truong
+    Andreas Molzer
+    github:hashitaku
+    github:srdjanstipic
+    Macoy Madson
+    Andreas Vennstrom
+    Tobias Mansfield-Williams
+*/
+
+#ifdef STBDS_UNIT_TESTS
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+
+#ifndef INCLUDE_STB_DS_H
+#define INCLUDE_STB_DS_H
+
+#include <stddef.h>
+#include <string.h>
+
+#ifndef STBDS_NO_SHORT_NAMES
+#define arrlen      stbds_arrlen
+#define arrlenu     stbds_arrlenu
+#define arrput      stbds_arrput
+#define arrpush     stbds_arrput
+#define arrpop      stbds_arrpop
+#define arrfree     stbds_arrfree
+#define arraddn     stbds_arraddn // deprecated, use one of the following instead:
+#define arraddnptr  stbds_arraddnptr
+#define arraddnindex stbds_arraddnindex
+#define arrsetlen   stbds_arrsetlen
+#define arrlast     stbds_arrlast
+#define arrins      stbds_arrins
+#define arrinsn     stbds_arrinsn
+#define arrdel      stbds_arrdel
+#define arrdeln     stbds_arrdeln
+#define arrdelswap  stbds_arrdelswap
+#define arrcap      stbds_arrcap
+#define arrsetcap   stbds_arrsetcap
+
+#define hmput       stbds_hmput
+#define hmputs      stbds_hmputs
+#define hmget       stbds_hmget
+#define hmget_ts    stbds_hmget_ts
+#define hmgets      stbds_hmgets
+#define hmgetp      stbds_hmgetp
+#define hmgetp_ts   stbds_hmgetp_ts
+#define hmgetp_null stbds_hmgetp_null
+#define hmgeti      stbds_hmgeti
+#define hmgeti_ts   stbds_hmgeti_ts
+#define hmdel       stbds_hmdel
+#define hmlen       stbds_hmlen
+#define hmlenu      stbds_hmlenu
+#define hmfree      stbds_hmfree
+#define hmdefault   stbds_hmdefault
+#define hmdefaults  stbds_hmdefaults
+
+#define shput       stbds_shput
+#define shputi      stbds_shputi
+#define shputs      stbds_shputs
+#define shget       stbds_shget
+#define shgeti      stbds_shgeti
+#define shgets      stbds_shgets
+#define shgetp      stbds_shgetp
+#define shgetp_null stbds_shgetp_null
+#define shdel       stbds_shdel
+#define shlen       stbds_shlen
+#define shlenu      stbds_shlenu
+#define shfree      stbds_shfree
+#define shdefault   stbds_shdefault
+#define shdefaults  stbds_shdefaults
+#define sh_new_arena  stbds_sh_new_arena
+#define sh_new_strdup stbds_sh_new_strdup
+
+#define stralloc    stbds_stralloc
+#define strreset    stbds_strreset
+#endif
+
+#if defined(STBDS_REALLOC) && !defined(STBDS_FREE) || !defined(STBDS_REALLOC) && defined(STBDS_FREE)
+#error "You must define both STBDS_REALLOC and STBDS_FREE, or neither."
+#endif
+#if !defined(STBDS_REALLOC) && !defined(STBDS_FREE)
+#include <stdlib.h>
+#define STBDS_REALLOC(c,p,s) realloc(p,s)
+#define STBDS_FREE(c,p)      free(p)
+#endif
+
+#ifdef _MSC_VER
+#define STBDS_NOTUSED(v)  (void)(v)
+#else
+#define STBDS_NOTUSED(v)  (void)sizeof(v)
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// for security against attackers, seed the library with a random number, at least time() but stronger is better
+extern void stbds_rand_seed(size_t seed);
+
+// these are the hash functions used internally if you want to test them or use them for other purposes
+extern size_t stbds_hash_bytes(void *p, size_t len, size_t seed);
+extern size_t stbds_hash_string(char *str, size_t seed);
+
+// this is a simple string arena allocator, initialize with e.g. 'stbds_string_arena my_arena={0}'.
+typedef struct stbds_string_arena stbds_string_arena;
+extern char * stbds_stralloc(stbds_string_arena *a, char *str);
+extern void   stbds_strreset(stbds_string_arena *a);
+
+// have to #define STBDS_UNIT_TESTS to call this
+extern void stbds_unit_tests(void);
+
+///////////////
+//
+// Everything below here is implementation details
+//
+
+extern void * stbds_arrgrowf(void *a, size_t elemsize, size_t addlen, size_t min_cap);
+extern void   stbds_arrfreef(void *a);
+extern void   stbds_hmfree_func(void *p, size_t elemsize);
+extern void * stbds_hmget_key(void *a, size_t elemsize, void *key, size_t keysize, int mode);
+extern void * stbds_hmget_key_ts(void *a, size_t elemsize, void *key, size_t keysize, ptrdiff_t *temp, int mode);
+extern void * stbds_hmput_default(void *a, size_t elemsize);
+extern void * stbds_hmput_key(void *a, size_t elemsize, void *key, size_t keysize, int mode);
+extern void * stbds_hmdel_key(void *a, size_t elemsize, void *key, size_t keysize, size_t keyoffset, int mode);
+extern void * stbds_shmode_func(size_t elemsize, int mode);
+
+#ifdef __cplusplus
+}
+#endif
+
+#if defined(__GNUC__) || defined(__clang__)
+#define STBDS_HAS_TYPEOF
+#ifdef __cplusplus
+//#define STBDS_HAS_LITERAL_ARRAY  // this is currently broken for clang
+#endif
+#endif
+
+#if !defined(__cplusplus)
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
+#define STBDS_HAS_LITERAL_ARRAY
+#endif
+#endif
+
+// this macro takes the address of the argument, but on gcc/clang can accept rvalues
+#if defined(STBDS_HAS_LITERAL_ARRAY) && defined(STBDS_HAS_TYPEOF)
+  #if __clang__
+  #define STBDS_ADDRESSOF(typevar, value)     ((__typeof__(typevar)[1]){value}) // literal array decays to pointer to value
+  #else
+  #define STBDS_ADDRESSOF(typevar, value)     ((typeof(typevar)[1]){value}) // literal array decays to pointer to value
+  #endif
+#else
+#define STBDS_ADDRESSOF(typevar, value)     &(value)
+#endif
+
+#define STBDS_OFFSETOF(var,field)           ((char *) &(var)->field - (char *) (var))
+
+#define stbds_header(t)  ((stbds_array_header *) (t) - 1)
+#define stbds_temp(t)    stbds_header(t)->temp
+#define stbds_temp_key(t) (*(char **) stbds_header(t)->hash_table)
+
+#define stbds_arrsetcap(a,n)   (stbds_arrgrow(a,0,n))
+#define stbds_arrsetlen(a,n)   ((stbds_arrcap(a) < (size_t) (n) ? stbds_arrsetcap((a),(size_t)(n)),0 : 0), (a) ? stbds_header(a)->length = (size_t) (n) : 0)
+#define stbds_arrcap(a)        ((a) ? stbds_header(a)->capacity : 0)
+#define stbds_arrlen(a)        ((a) ? (ptrdiff_t) stbds_header(a)->length : 0)
+#define stbds_arrlenu(a)       ((a) ?             stbds_header(a)->length : 0)
+#define stbds_arrput(a,v)      (stbds_arrmaybegrow(a,1), (a)[stbds_header(a)->length++] = (v))
+#define stbds_arrpush          stbds_arrput  // synonym
+#define stbds_arrpop(a)        (stbds_header(a)->length--, (a)[stbds_header(a)->length])
+#define stbds_arraddn(a,n)     ((void)(stbds_arraddnindex(a, n)))    // deprecated, use one of the following instead:
+#define stbds_arraddnptr(a,n)  (stbds_arrmaybegrow(a,n), (n) ? (stbds_header(a)->length += (n), &(a)[stbds_header(a)->length-(n)]) : (a))
+#define stbds_arraddnindex(a,n)(stbds_arrmaybegrow(a,n), (n) ? (stbds_header(a)->length += (n), stbds_header(a)->length-(n)) : stbds_arrlen(a))
+#define stbds_arraddnoff       stbds_arraddnindex
+#define stbds_arrlast(a)       ((a)[stbds_header(a)->length-1])
+#define stbds_arrfree(a)       ((void) ((a) ? STBDS_FREE(NULL,stbds_header(a)) : (void)0), (a)=NULL)
+#define stbds_arrdel(a,i)      stbds_arrdeln(a,i,1)
+#define stbds_arrdeln(a,i,n)   (memmove(&(a)[i], &(a)[(i)+(n)], sizeof *(a) * (stbds_header(a)->length-(n)-(i))), stbds_header(a)->length -= (n))
+#define stbds_arrdelswap(a,i)  ((a)[i] = stbds_arrlast(a), stbds_header(a)->length -= 1)
+#define stbds_arrinsn(a,i,n)   (stbds_arraddn((a),(n)), memmove(&(a)[(i)+(n)], &(a)[i], sizeof *(a) * (stbds_header(a)->length-(n)-(i))))
+#define stbds_arrins(a,i,v)    (stbds_arrinsn((a),(i),1), (a)[i]=(v))
+
+#define stbds_arrmaybegrow(a,n)  ((!(a) || stbds_header(a)->length + (n) > stbds_header(a)->capacity) \
+                                  ? (stbds_arrgrow(a,n,0),0) : 0)
+
+#define stbds_arrgrow(a,b,c)   ((a) = stbds_arrgrowf_wrapper((a), sizeof *(a), (b), (c)))
+
+#define stbds_hmput(t, k, v) \
+    ((t) = stbds_hmput_key_wrapper((t), sizeof *(t), (void*) STBDS_ADDRESSOF((t)->key, (k)), sizeof (t)->key, 0),   \
+     (t)[stbds_temp((t)-1)].key = (k),    \
+     (t)[stbds_temp((t)-1)].value = (v))
+
+#define stbds_hmputs(t, s) \
+    ((t) = stbds_hmput_key_wrapper((t), sizeof *(t), &(s).key, sizeof (s).key, STBDS_HM_BINARY), \
+     (t)[stbds_temp((t)-1)] = (s))
+
+#define stbds_hmgeti(t,k) \
+    ((t) = stbds_hmget_key_wrapper((t), sizeof *(t), (void*) STBDS_ADDRESSOF((t)->key, (k)), sizeof (t)->key, STBDS_HM_BINARY), \
+      stbds_temp((t)-1))
+
+#define stbds_hmgeti_ts(t,k,temp) \
+    ((t) = stbds_hmget_key_ts_wrapper((t), sizeof *(t), (void*) STBDS_ADDRESSOF((t)->key, (k)), sizeof (t)->key, &(temp), STBDS_HM_BINARY), \
+      (temp))
+
+#define stbds_hmgetp(t, k) \
+    ((void) stbds_hmgeti(t,k), &(t)[stbds_temp((t)-1)])
+
+#define stbds_hmgetp_ts(t, k, temp) \
+    ((void) stbds_hmgeti_ts(t,k,temp), &(t)[temp])
+
+#define stbds_hmdel(t,k) \
+    (((t) = stbds_hmdel_key_wrapper((t),sizeof *(t), (void*) STBDS_ADDRESSOF((t)->key, (k)), sizeof (t)->key, STBDS_OFFSETOF((t),key), STBDS_HM_BINARY)),(t)?stbds_temp((t)-1):0)
+
+#define stbds_hmdefault(t, v) \
+    ((t) = stbds_hmput_default_wrapper((t), sizeof *(t)), (t)[-1].value = (v))
+
+#define stbds_hmdefaults(t, s) \
+    ((t) = stbds_hmput_default_wrapper((t), sizeof *(t)), (t)[-1] = (s))
+
+#define stbds_hmfree(p)        \
+    ((void) ((p) != NULL ? stbds_hmfree_func((p)-1,sizeof*(p)),0 : 0),(p)=NULL)
+
+#define stbds_hmgets(t, k)    (*stbds_hmgetp(t,k))
+#define stbds_hmget(t, k)     (stbds_hmgetp(t,k)->value)
+#define stbds_hmget_ts(t, k, temp)  (stbds_hmgetp_ts(t,k,temp)->value)
+#define stbds_hmlen(t)        ((t) ? (ptrdiff_t) stbds_header((t)-1)->length-1 : 0)
+#define stbds_hmlenu(t)       ((t) ?             stbds_header((t)-1)->length-1 : 0)
+#define stbds_hmgetp_null(t,k)  (stbds_hmgeti(t,k) == -1 ? NULL : &(t)[stbds_temp((t)-1)])
+
+#define stbds_shput(t, k, v) \
+    ((t) = stbds_hmput_key_wrapper((t), sizeof *(t), (void*) (k), sizeof (t)->key, STBDS_HM_STRING),   \
+     (t)[stbds_temp((t)-1)].value = (v))
+
+#define stbds_shputi(t, k, v) \
+    ((t) = stbds_hmput_key_wrapper((t), sizeof *(t), (void*) (k), sizeof (t)->key, STBDS_HM_STRING),   \
+     (t)[stbds_temp((t)-1)].value = (v), stbds_temp((t)-1))
+
+#define stbds_shputs(t, s) \
+    ((t) = stbds_hmput_key_wrapper((t), sizeof *(t), (void*) (s).key, sizeof (s).key, STBDS_HM_STRING), \
+     (t)[stbds_temp((t)-1)] = (s), \
+     (t)[stbds_temp((t)-1)].key = stbds_temp_key((t)-1)) // above line overwrites whole structure, so must rewrite key here if it was allocated internally
+
+#define stbds_pshput(t, p) \
+    ((t) = stbds_hmput_key_wrapper((t), sizeof *(t), (void*) (p)->key, sizeof (p)->key, STBDS_HM_PTR_TO_STRING), \
+     (t)[stbds_temp((t)-1)] = (p))
+
+#define stbds_shgeti(t,k) \
+     ((t) = stbds_hmget_key_wrapper((t), sizeof *(t), (void*) (k), sizeof (t)->key, STBDS_HM_STRING), \
+      stbds_temp((t)-1))
+
+#define stbds_pshgeti(t,k) \
+     ((t) = stbds_hmget_key_wrapper((t), sizeof *(t), (void*) (k), sizeof (*(t))->key, STBDS_HM_PTR_TO_STRING), \
+      stbds_temp((t)-1))
+
+#define stbds_shgetp(t, k) \
+    ((void) stbds_shgeti(t,k), &(t)[stbds_temp((t)-1)])
+
+#define stbds_pshget(t, k) \
+    ((void) stbds_pshgeti(t,k), (t)[stbds_temp((t)-1)])
+
+#define stbds_shdel(t,k) \
+    (((t) = stbds_hmdel_key_wrapper((t),sizeof *(t), (void*) (k), sizeof (t)->key, STBDS_OFFSETOF((t),key), STBDS_HM_STRING)),(t)?stbds_temp((t)-1):0)
+#define stbds_pshdel(t,k) \
+    (((t) = stbds_hmdel_key_wrapper((t),sizeof *(t), (void*) (k), sizeof (*(t))->key, STBDS_OFFSETOF(*(t),key), STBDS_HM_PTR_TO_STRING)),(t)?stbds_temp((t)-1):0)
+
+#define stbds_sh_new_arena(t)  \
+    ((t) = stbds_shmode_func_wrapper(t, sizeof *(t), STBDS_SH_ARENA))
+#define stbds_sh_new_strdup(t) \
+    ((t) = stbds_shmode_func_wrapper(t, sizeof *(t), STBDS_SH_STRDUP))
+
+#define stbds_shdefault(t, v)  stbds_hmdefault(t,v)
+#define stbds_shdefaults(t, s) stbds_hmdefaults(t,s)
+
+#define stbds_shfree       stbds_hmfree
+#define stbds_shlenu       stbds_hmlenu
+
+#define stbds_shgets(t, k) (*stbds_shgetp(t,k))
+#define stbds_shget(t, k)  (stbds_shgetp(t,k)->value)
+#define stbds_shgetp_null(t,k)  (stbds_shgeti(t,k) == -1 ? NULL : &(t)[stbds_temp((t)-1)])
+#define stbds_shlen        stbds_hmlen
+
+typedef struct
+{
+  size_t      length;
+  size_t      capacity;
+  void      * hash_table;
+  ptrdiff_t   temp;
+} stbds_array_header;
+
+typedef struct stbds_string_block
+{
+  struct stbds_string_block *next;
+  char storage[8];
+} stbds_string_block;
+
+struct stbds_string_arena
+{
+  stbds_string_block *storage;
+  size_t remaining;
+  unsigned char block;
+  unsigned char mode;  // this isn't used by the string arena itself
+};
+
+#define STBDS_HM_BINARY         0
+#define STBDS_HM_STRING         1
+
+enum
+{
+   STBDS_SH_NONE,
+   STBDS_SH_DEFAULT,
+   STBDS_SH_STRDUP,
+   STBDS_SH_ARENA
+};
+
+#ifdef __cplusplus
+// in C we use implicit assignment from these void*-returning functions to T*.
+// in C++ these templates make the same code work
+template<class T> static T * stbds_arrgrowf_wrapper(T *a, size_t elemsize, size_t addlen, size_t min_cap) {
+  return (T*)stbds_arrgrowf((void *)a, elemsize, addlen, min_cap);
+}
+template<class T> static T * stbds_hmget_key_wrapper(T *a, size_t elemsize, void *key, size_t keysize, int mode) {
+  return (T*)stbds_hmget_key((void*)a, elemsize, key, keysize, mode);
+}
+template<class T> static T * stbds_hmget_key_ts_wrapper(T *a, size_t elemsize, void *key, size_t keysize, ptrdiff_t *temp, int mode) {
+  return (T*)stbds_hmget_key_ts((void*)a, elemsize, key, keysize, temp, mode);
+}
+template<class T> static T * stbds_hmput_default_wrapper(T *a, size_t elemsize) {
+  return (T*)stbds_hmput_default((void *)a, elemsize);
+}
+template<class T> static T * stbds_hmput_key_wrapper(T *a, size_t elemsize, void *key, size_t keysize, int mode) {
+  return (T*)stbds_hmput_key((void*)a, elemsize, key, keysize, mode);
+}
+template<class T> static T * stbds_hmdel_key_wrapper(T *a, size_t elemsize, void *key, size_t keysize, size_t keyoffset, int mode){
+  return (T*)stbds_hmdel_key((void*)a, elemsize, key, keysize, keyoffset, mode);
+}
+template<class T> static T * stbds_shmode_func_wrapper(T *, size_t elemsize, int mode) {
+  return (T*)stbds_shmode_func(elemsize, mode);
+}
+#else
+#define stbds_arrgrowf_wrapper            stbds_arrgrowf
+#define stbds_hmget_key_wrapper           stbds_hmget_key
+#define stbds_hmget_key_ts_wrapper        stbds_hmget_key_ts
+#define stbds_hmput_default_wrapper       stbds_hmput_default
+#define stbds_hmput_key_wrapper           stbds_hmput_key
+#define stbds_hmdel_key_wrapper           stbds_hmdel_key
+#define stbds_shmode_func_wrapper(t,e,m)  stbds_shmode_func(e,m)
+#endif
+
+#endif // INCLUDE_STB_DS_H
+
+
+//////////////////////////////////////////////////////////////////////////////
+//
+//   IMPLEMENTATION
+//
+
+#ifdef STB_DS_IMPLEMENTATION
+#include <assert.h>
+#include <string.h>
+
+#ifndef STBDS_ASSERT
+#define STBDS_ASSERT_WAS_UNDEFINED
+#define STBDS_ASSERT(x)   ((void) 0)
+#endif
+
+#ifdef STBDS_STATISTICS
+#define STBDS_STATS(x)   x
+size_t stbds_array_grow;
+size_t stbds_hash_grow;
+size_t stbds_hash_shrink;
+size_t stbds_hash_rebuild;
+size_t stbds_hash_probes;
+size_t stbds_hash_alloc;
+size_t stbds_rehash_probes;
+size_t stbds_rehash_items;
+#else
+#define STBDS_STATS(x)
+#endif
+
+//
+// stbds_arr implementation
+//
+
+//int *prev_allocs[65536];
+//int num_prev;
+
+void *stbds_arrgrowf(void *a, size_t elemsize, size_t addlen, size_t min_cap)
+{
+  stbds_array_header temp={0}; // force debugging
+  void *b;
+  size_t min_len = stbds_arrlen(a) + addlen;
+  (void) sizeof(temp);
+
+  // compute the minimum capacity needed
+  if (min_len > min_cap)
+    min_cap = min_len;
+
+  if (min_cap <= stbds_arrcap(a))
+    return a;
+
+  // increase needed capacity to guarantee O(1) amortized
+  if (min_cap < 2 * stbds_arrcap(a))
+    min_cap = 2 * stbds_arrcap(a);
+  else if (min_cap < 4)
+    min_cap = 4;
+
+  //if (num_prev < 65536) if (a) prev_allocs[num_prev++] = (int *) ((char *) a+1);
+  //if (num_prev == 2201)
+  //  num_prev = num_prev;
+  b = STBDS_REALLOC(NULL, (a) ? stbds_header(a) : 0, elemsize * min_cap + sizeof(stbds_array_header));
+  //if (num_prev < 65536) prev_allocs[num_prev++] = (int *) (char *) b;
+  b = (char *) b + sizeof(stbds_array_header);
+  if (a == NULL) {
+    stbds_header(b)->length = 0;
+    stbds_header(b)->hash_table = 0;
+    stbds_header(b)->temp = 0;
+  } else {
+    STBDS_STATS(++stbds_array_grow);
+  }
+  stbds_header(b)->capacity = min_cap;
+
+  return b;
+}
+
+void stbds_arrfreef(void *a)
+{
+  STBDS_FREE(NULL, stbds_header(a));
+}
+
+//
+// stbds_hm hash table implementation
+//
+
+#ifdef STBDS_INTERNAL_SMALL_BUCKET
+#define STBDS_BUCKET_LENGTH      4
+#else
+#define STBDS_BUCKET_LENGTH      8
+#endif
+
+#define STBDS_BUCKET_SHIFT      (STBDS_BUCKET_LENGTH == 8 ? 3 : 2)
+#define STBDS_BUCKET_MASK       (STBDS_BUCKET_LENGTH-1)
+#define STBDS_CACHE_LINE_SIZE   64
+
+#define STBDS_ALIGN_FWD(n,a)   (((n) + (a) - 1) & ~((a)-1))
+
+typedef struct
+{
+   size_t    hash [STBDS_BUCKET_LENGTH];
+   ptrdiff_t index[STBDS_BUCKET_LENGTH];
+} stbds_hash_bucket; // in 32-bit, this is one 64-byte cache line; in 64-bit, each array is one 64-byte cache line
+
+typedef struct
+{
+  char * temp_key; // this MUST be the first field of the hash table
+  size_t slot_count;
+  size_t used_count;
+  size_t used_count_threshold;
+  size_t used_count_shrink_threshold;
+  size_t tombstone_count;
+  size_t tombstone_count_threshold;
+  size_t seed;
+  size_t slot_count_log2;
+  stbds_string_arena string;
+  stbds_hash_bucket *storage; // not a separate allocation, just 64-byte aligned storage after this struct
+} stbds_hash_index;
+
+#define STBDS_INDEX_EMPTY    -1
+#define STBDS_INDEX_DELETED  -2
+#define STBDS_INDEX_IN_USE(x)  ((x) >= 0)
+
+#define STBDS_HASH_EMPTY      0
+#define STBDS_HASH_DELETED    1
+
+static size_t stbds_hash_seed=0x31415926;
+
+void stbds_rand_seed(size_t seed)
+{
+  stbds_hash_seed = seed;
+}
+
+#define stbds_load_32_or_64(var, temp, v32, v64_hi, v64_lo)                                          \
+  temp = v64_lo ^ v32, temp <<= 16, temp <<= 16, temp >>= 16, temp >>= 16, /* discard if 32-bit */   \
+  var = v64_hi, var <<= 16, var <<= 16,                                    /* discard if 32-bit */   \
+  var ^= temp ^ v32
+
+#define STBDS_SIZE_T_BITS           ((sizeof (size_t)) * 8)
+
+static size_t stbds_probe_position(size_t hash, size_t slot_count, size_t slot_log2)
+{
+  size_t pos;
+  STBDS_NOTUSED(slot_log2);
+  pos = hash & (slot_count-1);
+  #ifdef STBDS_INTERNAL_BUCKET_START
+  pos &= ~STBDS_BUCKET_MASK;
+  #endif
+  return pos;
+}
+
+static size_t stbds_log2(size_t slot_count)
+{
+  size_t n=0;
+  while (slot_count > 1) {
+    slot_count >>= 1;
+    ++n;
+  }
+  return n;
+}
+
+static stbds_hash_index *stbds_make_hash_index(size_t slot_count, stbds_hash_index *ot)
+{
+  stbds_hash_index *t;
+  t = (stbds_hash_index *) STBDS_REALLOC(NULL,0,(slot_count >> STBDS_BUCKET_SHIFT) * sizeof(stbds_hash_bucket) + sizeof(stbds_hash_index) + STBDS_CACHE_LINE_SIZE-1);
+  t->storage = (stbds_hash_bucket *) STBDS_ALIGN_FWD((size_t) (t+1), STBDS_CACHE_LINE_SIZE);
+  t->slot_count = slot_count;
+  t->slot_count_log2 = stbds_log2(slot_count);
+  t->tombstone_count = 0;
+  t->used_count = 0;
+
+  #if 0 // A1
+  t->used_count_threshold        = slot_count*12/16; // if 12/16th of table is occupied, grow
+  t->tombstone_count_threshold   = slot_count* 2/16; // if tombstones are 2/16th of table, rebuild
+  t->used_count_shrink_threshold = slot_count* 4/16; // if table is only 4/16th full, shrink
+  #elif 1 // A2
+  //t->used_count_threshold        = slot_count*12/16; // if 12/16th of table is occupied, grow
+  //t->tombstone_count_threshold   = slot_count* 3/16; // if tombstones are 3/16th of table, rebuild
+  //t->used_count_shrink_threshold = slot_count* 4/16; // if table is only 4/16th full, shrink
+
+  // compute without overflowing
+  t->used_count_threshold        = slot_count - (slot_count>>2);
+  t->tombstone_count_threshold   = (slot_count>>3) + (slot_count>>4);
+  t->used_count_shrink_threshold = slot_count >> 2;
+
+  #elif 0 // B1
+  t->used_count_threshold        = slot_count*13/16; // if 13/16th of table is occupied, grow
+  t->tombstone_count_threshold   = slot_count* 2/16; // if tombstones are 2/16th of table, rebuild
+  t->used_count_shrink_threshold = slot_count* 5/16; // if table is only 5/16th full, shrink
+  #else // C1
+  t->used_count_threshold        = slot_count*14/16; // if 14/16th of table is occupied, grow
+  t->tombstone_count_threshold   = slot_count* 2/16; // if tombstones are 2/16th of table, rebuild
+  t->used_count_shrink_threshold = slot_count* 6/16; // if table is only 6/16th full, shrink
+  #endif
+  // Following statistics were measured on a Core i7-6700 @ 4.00Ghz, compiled with clang 7.0.1 -O2
+    // Note that the larger tables have high variance as they were run fewer times
+  //     A1            A2          B1           C1
+  //    0.10ms :     0.10ms :     0.10ms :     0.11ms :      2,000 inserts creating 2K table
+  //    0.96ms :     0.95ms :     0.97ms :     1.04ms :     20,000 inserts creating 20K table
+  //   14.48ms :    14.46ms :    10.63ms :    11.00ms :    200,000 inserts creating 200K table
+  //  195.74ms :   196.35ms :   203.69ms :   214.92ms :  2,000,000 inserts creating 2M table
+  // 2193.88ms :  2209.22ms :  2285.54ms :  2437.17ms : 20,000,000 inserts creating 20M table
+  //   65.27ms :    53.77ms :    65.33ms :    65.47ms : 500,000 inserts & deletes in 2K table
+  //   72.78ms :    62.45ms :    71.95ms :    72.85ms : 500,000 inserts & deletes in 20K table
+  //   89.47ms :    77.72ms :    96.49ms :    96.75ms : 500,000 inserts & deletes in 200K table
+  //   97.58ms :    98.14ms :    97.18ms :    97.53ms : 500,000 inserts & deletes in 2M table
+  //  118.61ms :   119.62ms :   120.16ms :   118.86ms : 500,000 inserts & deletes in 20M table
+  //  192.11ms :   194.39ms :   196.38ms :   195.73ms : 500,000 inserts & deletes in 200M table
+
+  if (slot_count <= STBDS_BUCKET_LENGTH)
+    t->used_count_shrink_threshold = 0;
+  // to avoid infinite loop, we need to guarantee that at least one slot is empty and will terminate probes
+  STBDS_ASSERT(t->used_count_threshold + t->tombstone_count_threshold < t->slot_count);
+  STBDS_STATS(++stbds_hash_alloc);
+  if (ot) {
+    t->string = ot->string;
+    // reuse old seed so we can reuse old hashes so below "copy out old data" doesn't do any hashing
+    t->seed = ot->seed;
+  } else {
+    size_t a,b,temp;
+    memset(&t->string, 0, sizeof(t->string));
+    t->seed = stbds_hash_seed;
+    // LCG
+    // in 32-bit, a =          2147001325   b =  715136305
+    // in 64-bit, a = 2862933555777941757   b = 3037000493
+    stbds_load_32_or_64(a,temp, 2147001325, 0x27bb2ee6, 0x87b0b0fd);
+    stbds_load_32_or_64(b,temp,  715136305,          0, 0xb504f32d);
+    stbds_hash_seed = stbds_hash_seed  * a + b;
+  }
+
+  {
+    size_t i,j;
+    for (i=0; i < slot_count >> STBDS_BUCKET_SHIFT; ++i) {
+      stbds_hash_bucket *b = &t->storage[i];
+      for (j=0; j < STBDS_BUCKET_LENGTH; ++j)
+        b->hash[j] = STBDS_HASH_EMPTY;
+      for (j=0; j < STBDS_BUCKET_LENGTH; ++j)
+        b->index[j] = STBDS_INDEX_EMPTY;
+    }
+  }
+
+  // copy out the old data, if any
+  if (ot) {
+    size_t i,j;
+    t->used_count = ot->used_count;
+    for (i=0; i < ot->slot_count >> STBDS_BUCKET_SHIFT; ++i) {
+      stbds_hash_bucket *ob = &ot->storage[i];
+      for (j=0; j < STBDS_BUCKET_LENGTH; ++j) {
+        if (STBDS_INDEX_IN_USE(ob->index[j])) {
+          size_t hash = ob->hash[j];
+          size_t pos = stbds_probe_position(hash, t->slot_count, t->slot_count_log2);
+          size_t step = STBDS_BUCKET_LENGTH;
+          STBDS_STATS(++stbds_rehash_items);
+          for (;;) {
+            size_t limit,z;
+            stbds_hash_bucket *bucket;
+            bucket = &t->storage[pos >> STBDS_BUCKET_SHIFT];
+            STBDS_STATS(++stbds_rehash_probes);
+
+            for (z=pos & STBDS_BUCKET_MASK; z < STBDS_BUCKET_LENGTH; ++z) {
+              if (bucket->hash[z] == 0) {
+                bucket->hash[z] = hash;
+                bucket->index[z] = ob->index[j];
+                goto done;
+              }
+            }
+
+            limit = pos & STBDS_BUCKET_MASK;
+            for (z = 0; z < limit; ++z) {
+              if (bucket->hash[z] == 0) {
+                bucket->hash[z] = hash;
+                bucket->index[z] = ob->index[j];
+                goto done;
+              }
+            }
+
+            pos += step;                  // quadratic probing
+            step += STBDS_BUCKET_LENGTH;
+            pos &= (t->slot_count-1);
+          }
+        }
+       done:
+        ;
+      }
+    }
+  }
+
+  return t;
+}
+
+#define STBDS_ROTATE_LEFT(val, n)   (((val) << (n)) | ((val) >> (STBDS_SIZE_T_BITS - (n))))
+#define STBDS_ROTATE_RIGHT(val, n)  (((val) >> (n)) | ((val) << (STBDS_SIZE_T_BITS - (n))))
+
+size_t stbds_hash_string(char *str, size_t seed)
+{
+  size_t hash = seed;
+  while (*str)
+     hash = STBDS_ROTATE_LEFT(hash, 9) + (unsigned char) *str++;
+
+  // Thomas Wang 64-to-32 bit mix function, hopefully also works in 32 bits
+  hash ^= seed;
+  hash = (~hash) + (hash << 18);
+  hash ^= hash ^ STBDS_ROTATE_RIGHT(hash,31);
+  hash = hash * 21;
+  hash ^= hash ^ STBDS_ROTATE_RIGHT(hash,11);
+  hash += (hash << 6);
+  hash ^= STBDS_ROTATE_RIGHT(hash,22);
+  return hash+seed;
+}
+
+#ifdef STBDS_SIPHASH_2_4
+#define STBDS_SIPHASH_C_ROUNDS 2
+#define STBDS_SIPHASH_D_ROUNDS 4
+typedef int STBDS_SIPHASH_2_4_can_only_be_used_in_64_bit_builds[sizeof(size_t) == 8 ? 1 : -1];
+#endif
+
+#ifndef STBDS_SIPHASH_C_ROUNDS
+#define STBDS_SIPHASH_C_ROUNDS 1
+#endif
+#ifndef STBDS_SIPHASH_D_ROUNDS
+#define STBDS_SIPHASH_D_ROUNDS 1
+#endif
+
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable:4127) // conditional expression is constant, for do..while(0) and sizeof()==
+#endif
+
+static size_t stbds_siphash_bytes(void *p, size_t len, size_t seed)
+{
+  unsigned char *d = (unsigned char *) p;
+  size_t i,j;
+  size_t v0,v1,v2,v3, data;
+
+  // hash that works on 32- or 64-bit registers without knowing which we have
+  // (computes different results on 32-bit and 64-bit platform)
+  // derived from siphash, but on 32-bit platforms very different as it uses 4 32-bit state not 4 64-bit
+  v0 = ((((size_t) 0x736f6d65 << 16) << 16) + 0x70736575) ^  seed;
+  v1 = ((((size_t) 0x646f7261 << 16) << 16) + 0x6e646f6d) ^ ~seed;
+  v2 = ((((size_t) 0x6c796765 << 16) << 16) + 0x6e657261) ^  seed;
+  v3 = ((((size_t) 0x74656462 << 16) << 16) + 0x79746573) ^ ~seed;
+
+  #ifdef STBDS_TEST_SIPHASH_2_4
+  // hardcoded with key material in the siphash test vectors
+  v0 ^= 0x0706050403020100ull ^  seed;
+  v1 ^= 0x0f0e0d0c0b0a0908ull ^ ~seed;
+  v2 ^= 0x0706050403020100ull ^  seed;
+  v3 ^= 0x0f0e0d0c0b0a0908ull ^ ~seed;
+  #endif
+
+  #define STBDS_SIPROUND() \
+    do {                   \
+      v0 += v1; v1 = STBDS_ROTATE_LEFT(v1, 13);  v1 ^= v0; v0 = STBDS_ROTATE_LEFT(v0,STBDS_SIZE_T_BITS/2); \
+      v2 += v3; v3 = STBDS_ROTATE_LEFT(v3, 16);  v3 ^= v2;                                                 \
+      v2 += v1; v1 = STBDS_ROTATE_LEFT(v1, 17);  v1 ^= v2; v2 = STBDS_ROTATE_LEFT(v2,STBDS_SIZE_T_BITS/2); \
+      v0 += v3; v3 = STBDS_ROTATE_LEFT(v3, 21);  v3 ^= v0;                                                 \
+    } while (0)
+
+  for (i=0; i+sizeof(size_t) <= len; i += sizeof(size_t), d += sizeof(size_t)) {
+    data = d[0] | (d[1] << 8) | (d[2] << 16) | (d[3] << 24);
+    data |= (size_t) (d[4] | (d[5] << 8) | (d[6] << 16) | (d[7] << 24)) << 16 << 16; // discarded if size_t == 4
+
+    v3 ^= data;
+    for (j=0; j < STBDS_SIPHASH_C_ROUNDS; ++j)
+      STBDS_SIPROUND();
+    v0 ^= data;
+  }
+  data = len << (STBDS_SIZE_T_BITS-8);
+  switch (len - i) {
+    case 7: data |= ((size_t) d[6] << 24) << 24; // fall through
+    case 6: data |= ((size_t) d[5] << 20) << 20; // fall through
+    case 5: data |= ((size_t) d[4] << 16) << 16; // fall through
+    case 4: data |= (d[3] << 24); // fall through
+    case 3: data |= (d[2] << 16); // fall through
+    case 2: data |= (d[1] << 8); // fall through
+    case 1: data |= d[0]; // fall through
+    case 0: break;
+  }
+  v3 ^= data;
+  for (j=0; j < STBDS_SIPHASH_C_ROUNDS; ++j)
+    STBDS_SIPROUND();
+  v0 ^= data;
+  v2 ^= 0xff;
+  for (j=0; j < STBDS_SIPHASH_D_ROUNDS; ++j)
+    STBDS_SIPROUND();
+
+#ifdef STBDS_SIPHASH_2_4
+  return v0^v1^v2^v3;
+#else
+  return v1^v2^v3; // slightly stronger since v0^v3 in above cancels out final round operation? I tweeted at the authors of SipHash about this but they didn't reply
+#endif
+}
+
+size_t stbds_hash_bytes(void *p, size_t len, size_t seed)
+{
+#ifdef STBDS_SIPHASH_2_4
+  return stbds_siphash_bytes(p,len,seed);
+#else
+  unsigned char *d = (unsigned char *) p;
+
+  if (len == 4) {
+    unsigned int hash = d[0] | (d[1] << 8) | (d[2] << 16) | (d[3] << 24);
+    #if 0
+    // HASH32-A  Bob Jenkin's hash function w/o large constants
+    hash ^= seed;
+    hash -= (hash<<6);
+    hash ^= (hash>>17);
+    hash -= (hash<<9);
+    hash ^= seed;
+    hash ^= (hash<<4);
+    hash -= (hash<<3);
+    hash ^= (hash<<10);
+    hash ^= (hash>>15);
+    #elif 1
+    // HASH32-BB  Bob Jenkin's presumably-accidental version of Thomas Wang hash with rotates turned into shifts.
+    // Note that converting these back to rotates makes it run a lot slower, presumably due to collisions, so I'm
+    // not really sure what's going on.
+    hash ^= seed;
+    hash = (hash ^ 61) ^ (hash >> 16);
+    hash = hash + (hash << 3);
+    hash = hash ^ (hash >> 4);
+    hash = hash * 0x27d4eb2d;
+    hash ^= seed;
+    hash = hash ^ (hash >> 15);
+    #else  // HASH32-C   -  Murmur3
+    hash ^= seed;
+    hash *= 0xcc9e2d51;
+    hash = (hash << 17) | (hash >> 15);
+    hash *= 0x1b873593;
+    hash ^= seed;
+    hash = (hash << 19) | (hash >> 13);
+    hash = hash*5 + 0xe6546b64;
+    hash ^= hash >> 16;
+    hash *= 0x85ebca6b;
+    hash ^= seed;
+    hash ^= hash >> 13;
+    hash *= 0xc2b2ae35;
+    hash ^= hash >> 16;
+    #endif
+    // Following statistics were measured on a Core i7-6700 @ 4.00Ghz, compiled with clang 7.0.1 -O2
+    // Note that the larger tables have high variance as they were run fewer times
+    //  HASH32-A   //  HASH32-BB  //  HASH32-C
+    //    0.10ms   //    0.10ms   //    0.10ms :      2,000 inserts creating 2K table
+    //    0.96ms   //    0.95ms   //    0.99ms :     20,000 inserts creating 20K table
+    //   14.69ms   //   14.43ms   //   14.97ms :    200,000 inserts creating 200K table
+    //  199.99ms   //  195.36ms   //  202.05ms :  2,000,000 inserts creating 2M table
+    // 2234.84ms   // 2187.74ms   // 2240.38ms : 20,000,000 inserts creating 20M table
+    //   55.68ms   //   53.72ms   //   57.31ms : 500,000 inserts & deletes in 2K table
+    //   63.43ms   //   61.99ms   //   65.73ms : 500,000 inserts & deletes in 20K table
+    //   80.04ms   //   77.96ms   //   81.83ms : 500,000 inserts & deletes in 200K table
+    //  100.42ms   //   97.40ms   //  102.39ms : 500,000 inserts & deletes in 2M table
+    //  119.71ms   //  120.59ms   //  121.63ms : 500,000 inserts & deletes in 20M table
+    //  185.28ms   //  195.15ms   //  187.74ms : 500,000 inserts & deletes in 200M table
+    //   15.58ms   //   14.79ms   //   15.52ms : 200,000 inserts creating 200K table with varying key spacing
+
+    return (((size_t) hash << 16 << 16) | hash) ^ seed;
+  } else if (len == 8 && sizeof(size_t) == 8) {
+    size_t hash = d[0] | (d[1] << 8) | (d[2] << 16) | (d[3] << 24);
+    hash |= (size_t) (d[4] | (d[5] << 8) | (d[6] << 16) | (d[7] << 24)) << 16 << 16; // avoid warning if size_t == 4
+    hash ^= seed;
+    hash = (~hash) + (hash << 21);
+    hash ^= STBDS_ROTATE_RIGHT(hash,24);
+    hash *= 265;
+    hash ^= STBDS_ROTATE_RIGHT(hash,14);
+    hash ^= seed;
+    hash *= 21;
+    hash ^= STBDS_ROTATE_RIGHT(hash,28);
+    hash += (hash << 31);
+    hash = (~hash) + (hash << 18);
+    return hash;
+  } else {
+    return stbds_siphash_bytes(p,len,seed);
+  }
+#endif
+}
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+
+static int stbds_is_key_equal(void *a, size_t elemsize, void *key, size_t keysize, size_t keyoffset, int mode, size_t i)
+{
+  if (mode >= STBDS_HM_STRING)
+    return 0==strcmp((char *) key, * (char **) ((char *) a + elemsize*i + keyoffset));
+  else
+    return 0==memcmp(key, (char *) a + elemsize*i + keyoffset, keysize);
+}
+
+#define STBDS_HASH_TO_ARR(x,elemsize) ((char*) (x) - (elemsize))
+#define STBDS_ARR_TO_HASH(x,elemsize) ((char*) (x) + (elemsize))
+
+#define stbds_hash_table(a)  ((stbds_hash_index *) stbds_header(a)->hash_table)
+
+void stbds_hmfree_func(void *a, size_t elemsize)
+{
+  if (a == NULL) return;
+  if (stbds_hash_table(a) != NULL) {
+    if (stbds_hash_table(a)->string.mode == STBDS_SH_STRDUP) {
+      size_t i;
+      // skip 0th element, which is default
+      for (i=1; i < stbds_header(a)->length; ++i)
+        STBDS_FREE(NULL, *(char**) ((char *) a + elemsize*i));
+    }
+    stbds_strreset(&stbds_hash_table(a)->string);
+  }
+  STBDS_FREE(NULL, stbds_header(a)->hash_table);
+  STBDS_FREE(NULL, stbds_header(a));
+}
+
+static ptrdiff_t stbds_hm_find_slot(void *a, size_t elemsize, void *key, size_t keysize, size_t keyoffset, int mode)
+{
+  void *raw_a = STBDS_HASH_TO_ARR(a,elemsize);
+  stbds_hash_index *table = stbds_hash_table(raw_a);
+  size_t hash = mode >= STBDS_HM_STRING ? stbds_hash_string((char*)key,table->seed) : stbds_hash_bytes(key, keysize,table->seed);
+  size_t step = STBDS_BUCKET_LENGTH;
+  size_t limit,i;
+  size_t pos;
+  stbds_hash_bucket *bucket;
+
+  if (hash < 2) hash += 2; // stored hash values are forbidden from being 0, so we can detect empty slots
+
+  pos = stbds_probe_position(hash, table->slot_count, table->slot_count_log2);
+
+  for (;;) {
+    STBDS_STATS(++stbds_hash_probes);
+    bucket = &table->storage[pos >> STBDS_BUCKET_SHIFT];
+
+    // start searching from pos to end of bucket, this should help performance on small hash tables that fit in cache
+    for (i=pos & STBDS_BUCKET_MASK; i < STBDS_BUCKET_LENGTH; ++i) {
+      if (bucket->hash[i] == hash) {
+        if (stbds_is_key_equal(a, elemsize, key, keysize, keyoffset, mode, bucket->index[i])) {
+          return (pos & ~STBDS_BUCKET_MASK)+i;
+        }
+      } else if (bucket->hash[i] == STBDS_HASH_EMPTY) {
+        return -1;
+      }
+    }
+
+    // search from beginning of bucket to pos
+    limit = pos & STBDS_BUCKET_MASK;
+    for (i = 0; i < limit; ++i) {
+      if (bucket->hash[i] == hash) {
+        if (stbds_is_key_equal(a, elemsize, key, keysize, keyoffset, mode, bucket->index[i])) {
+          return (pos & ~STBDS_BUCKET_MASK)+i;
+        }
+      } else if (bucket->hash[i] == STBDS_HASH_EMPTY) {
+        return -1;
+      }
+    }
+
+    // quadratic probing
+    pos += step;
+    step += STBDS_BUCKET_LENGTH;
+    pos &= (table->slot_count-1);
+  }
+  /* NOTREACHED */
+}
+
+void * stbds_hmget_key_ts(void *a, size_t elemsize, void *key, size_t keysize, ptrdiff_t *temp, int mode)
+{
+  size_t keyoffset = 0;
+  if (a == NULL) {
+    // make it non-empty so we can return a temp
+    a = stbds_arrgrowf(0, elemsize, 0, 1);
+    stbds_header(a)->length += 1;
+    memset(a, 0, elemsize);
+    *temp = STBDS_INDEX_EMPTY;
+    // adjust a to point after the default element
+    return STBDS_ARR_TO_HASH(a,elemsize);
+  } else {
+    stbds_hash_index *table;
+    void *raw_a = STBDS_HASH_TO_ARR(a,elemsize);
+    // adjust a to point to the default element
+    table = (stbds_hash_index *) stbds_header(raw_a)->hash_table;
+    if (table == 0) {
+      *temp = -1;
+    } else {
+      ptrdiff_t slot = stbds_hm_find_slot(a, elemsize, key, keysize, keyoffset, mode);
+      if (slot < 0) {
+        *temp = STBDS_INDEX_EMPTY;
+      } else {
+        stbds_hash_bucket *b = &table->storage[slot >> STBDS_BUCKET_SHIFT];
+        *temp = b->index[slot & STBDS_BUCKET_MASK];
+      }
+    }
+    return a;
+  }
+}
+
+void * stbds_hmget_key(void *a, size_t elemsize, void *key, size_t keysize, int mode)
+{
+  ptrdiff_t temp;
+  void *p = stbds_hmget_key_ts(a, elemsize, key, keysize, &temp, mode);
+  stbds_temp(STBDS_HASH_TO_ARR(p,elemsize)) = temp;
+  return p;
+}
+
+void * stbds_hmput_default(void *a, size_t elemsize)
+{
+  // three cases:
+  //   a is NULL <- allocate
+  //   a has a hash table but no entries, because of shmode <- grow
+  //   a has entries <- do nothing
+  if (a == NULL || stbds_header(STBDS_HASH_TO_ARR(a,elemsize))->length == 0) {
+    a = stbds_arrgrowf(a ? STBDS_HASH_TO_ARR(a,elemsize) : NULL, elemsize, 0, 1);
+    stbds_header(a)->length += 1;
+    memset(a, 0, elemsize);
+    a=STBDS_ARR_TO_HASH(a,elemsize);
+  }
+  return a;
+}
+
+static char *stbds_strdup(char *str);
+
+void *stbds_hmput_key(void *a, size_t elemsize, void *key, size_t keysize, int mode)
+{
+  size_t keyoffset=0;
+  void *raw_a;
+  stbds_hash_index *table;
+
+  if (a == NULL) {
+    a = stbds_arrgrowf(0, elemsize, 0, 1);
+    memset(a, 0, elemsize);
+    stbds_header(a)->length += 1;
+    // adjust a to point AFTER the default element
+    a = STBDS_ARR_TO_HASH(a,elemsize);
+  }
+
+  // adjust a to point to the default element
+  raw_a = a;
+  a = STBDS_HASH_TO_ARR(a,elemsize);
+
+  table = (stbds_hash_index *) stbds_header(a)->hash_table;
+
+  if (table == NULL || table->used_count >= table->used_count_threshold) {
+    stbds_hash_index *nt;
+    size_t slot_count;
+
+    slot_count = (table == NULL) ? STBDS_BUCKET_LENGTH : table->slot_count*2;
+    nt = stbds_make_hash_index(slot_count, table);
+    if (table)
+      STBDS_FREE(NULL, table);
+    else
+      nt->string.mode = mode >= STBDS_HM_STRING ? STBDS_SH_DEFAULT : 0;
+    stbds_header(a)->hash_table = table = nt;
+    STBDS_STATS(++stbds_hash_grow);
+  }
+
+  // we iterate hash table explicitly because we want to track if we saw a tombstone
+  {
+    size_t hash = mode >= STBDS_HM_STRING ? stbds_hash_string((char*)key,table->seed) : stbds_hash_bytes(key, keysize,table->seed);
+    size_t step = STBDS_BUCKET_LENGTH;
+    size_t pos;
+    ptrdiff_t tombstone = -1;
+    stbds_hash_bucket *bucket;
+
+    // stored hash values are forbidden from being 0, so we can detect empty slots to early out quickly
+    if (hash < 2) hash += 2;
+
+    pos = stbds_probe_position(hash, table->slot_count, table->slot_count_log2);
+
+    for (;;) {
+      size_t limit, i;
+      STBDS_STATS(++stbds_hash_probes);
+      bucket = &table->storage[pos >> STBDS_BUCKET_SHIFT];
+
+      // start searching from pos to end of bucket
+      for (i=pos & STBDS_BUCKET_MASK; i < STBDS_BUCKET_LENGTH; ++i) {
+        if (bucket->hash[i] == hash) {
+          if (stbds_is_key_equal(raw_a, elemsize, key, keysize, keyoffset, mode, bucket->index[i])) {
+            stbds_temp(a) = bucket->index[i];
+            if (mode >= STBDS_HM_STRING)
+              stbds_temp_key(a) = * (char **) ((char *) raw_a + elemsize*bucket->index[i] + keyoffset);
+            return STBDS_ARR_TO_HASH(a,elemsize);
+          }
+        } else if (bucket->hash[i] == 0) {
+          pos = (pos & ~STBDS_BUCKET_MASK) + i;
+          goto found_empty_slot;
+        } else if (tombstone < 0) {
+          if (bucket->index[i] == STBDS_INDEX_DELETED)
+            tombstone = (ptrdiff_t) ((pos & ~STBDS_BUCKET_MASK) + i);
+        }
+      }
+
+      // search from beginning of bucket to pos
+      limit = pos & STBDS_BUCKET_MASK;
+      for (i = 0; i < limit; ++i) {
+        if (bucket->hash[i] == hash) {
+          if (stbds_is_key_equal(raw_a, elemsize, key, keysize, keyoffset, mode, bucket->index[i])) {
+            stbds_temp(a) = bucket->index[i];
+            return STBDS_ARR_TO_HASH(a,elemsize);
+          }
+        } else if (bucket->hash[i] == 0) {
+          pos = (pos & ~STBDS_BUCKET_MASK) + i;
+          goto found_empty_slot;
+        } else if (tombstone < 0) {
+          if (bucket->index[i] == STBDS_INDEX_DELETED)
+            tombstone = (ptrdiff_t) ((pos & ~STBDS_BUCKET_MASK) + i);
+        }
+      }
+
+      // quadratic probing
+      pos += step;
+      step += STBDS_BUCKET_LENGTH;
+      pos &= (table->slot_count-1);
+    }
+   found_empty_slot:
+    if (tombstone >= 0) {
+      pos = tombstone;
+      --table->tombstone_count;
+    }
+    ++table->used_count;
+
+    {
+      ptrdiff_t i = (ptrdiff_t) stbds_arrlen(a);
+      // we want to do stbds_arraddn(1), but we can't use the macros since we don't have something of the right type
+      if ((size_t) i+1 > stbds_arrcap(a))
+        *(void **) &a = stbds_arrgrowf(a, elemsize, 1, 0);
+      raw_a = STBDS_ARR_TO_HASH(a,elemsize);
+
+      STBDS_ASSERT((size_t) i+1 <= stbds_arrcap(a));
+      stbds_header(a)->length = i+1;
+      bucket = &table->storage[pos >> STBDS_BUCKET_SHIFT];
+      bucket->hash[pos & STBDS_BUCKET_MASK] = hash;
+      bucket->index[pos & STBDS_BUCKET_MASK] = i-1;
+      stbds_temp(a) = i-1;
+
+      switch (table->string.mode) {
+         case STBDS_SH_STRDUP:  stbds_temp_key(a) = *(char **) ((char *) a + elemsize*i) = stbds_strdup((char*) key); break;
+         case STBDS_SH_ARENA:   stbds_temp_key(a) = *(char **) ((char *) a + elemsize*i) = stbds_stralloc(&table->string, (char*)key); break;
+         case STBDS_SH_DEFAULT: stbds_temp_key(a) = *(char **) ((char *) a + elemsize*i) = (char *) key; break;
+         default:                memcpy((char *) a + elemsize*i, key, keysize); break;
+      }
+    }
+    return STBDS_ARR_TO_HASH(a,elemsize);
+  }
+}
+
+void * stbds_shmode_func(size_t elemsize, int mode)
+{
+  void *a = stbds_arrgrowf(0, elemsize, 0, 1);
+  stbds_hash_index *h;
+  memset(a, 0, elemsize);
+  stbds_header(a)->length = 1;
+  stbds_header(a)->hash_table = h = (stbds_hash_index *) stbds_make_hash_index(STBDS_BUCKET_LENGTH, NULL);
+  h->string.mode = (unsigned char) mode;
+  return STBDS_ARR_TO_HASH(a,elemsize);
+}
+
+void * stbds_hmdel_key(void *a, size_t elemsize, void *key, size_t keysize, size_t keyoffset, int mode)
+{
+  if (a == NULL) {
+    return 0;
+  } else {
+    stbds_hash_index *table;
+    void *raw_a = STBDS_HASH_TO_ARR(a,elemsize);
+    table = (stbds_hash_index *) stbds_header(raw_a)->hash_table;
+    stbds_temp(raw_a) = 0;
+    if (table == 0) {
+      return a;
+    } else {
+      ptrdiff_t slot;
+      slot = stbds_hm_find_slot(a, elemsize, key, keysize, keyoffset, mode);
+      if (slot < 0)
+        return a;
+      else {
+        stbds_hash_bucket *b = &table->storage[slot >> STBDS_BUCKET_SHIFT];
+        int i = slot & STBDS_BUCKET_MASK;
+        ptrdiff_t old_index = b->index[i];
+        ptrdiff_t final_index = (ptrdiff_t) stbds_arrlen(raw_a)-1-1; // minus one for the raw_a vs a, and minus one for 'last'
+        STBDS_ASSERT(slot < (ptrdiff_t) table->slot_count);
+        --table->used_count;
+        ++table->tombstone_count;
+        stbds_temp(raw_a) = 1;
+        STBDS_ASSERT(table->used_count >= 0);
+        //STBDS_ASSERT(table->tombstone_count < table->slot_count/4);
+        b->hash[i] = STBDS_HASH_DELETED;
+        b->index[i] = STBDS_INDEX_DELETED;
+
+        if (mode == STBDS_HM_STRING && table->string.mode == STBDS_SH_STRDUP)
+          STBDS_FREE(NULL, *(char**) ((char *) a+elemsize*old_index));
+
+        // if indices are the same, memcpy is a no-op, but back-pointer-fixup will fail, so skip
+        if (old_index != final_index) {
+          // swap delete
+          memmove((char*) a + elemsize*old_index, (char*) a + elemsize*final_index, elemsize);
+
+          // now find the slot for the last element
+          if (mode == STBDS_HM_STRING)
+            slot = stbds_hm_find_slot(a, elemsize, *(char**) ((char *) a+elemsize*old_index + keyoffset), keysize, keyoffset, mode);
+          else
+            slot = stbds_hm_find_slot(a, elemsize,  (char* ) a+elemsize*old_index + keyoffset, keysize, keyoffset, mode);
+          STBDS_ASSERT(slot >= 0);
+          b = &table->storage[slot >> STBDS_BUCKET_SHIFT];
+          i = slot & STBDS_BUCKET_MASK;
+          STBDS_ASSERT(b->index[i] == final_index);
+          b->index[i] = old_index;
+        }
+        stbds_header(raw_a)->length -= 1;
+
+        if (table->used_count < table->used_count_shrink_threshold && table->slot_count > STBDS_BUCKET_LENGTH) {
+          stbds_header(raw_a)->hash_table = stbds_make_hash_index(table->slot_count>>1, table);
+          STBDS_FREE(NULL, table);
+          STBDS_STATS(++stbds_hash_shrink);
+        } else if (table->tombstone_count > table->tombstone_count_threshold) {
+          stbds_header(raw_a)->hash_table = stbds_make_hash_index(table->slot_count   , table);
+          STBDS_FREE(NULL, table);
+          STBDS_STATS(++stbds_hash_rebuild);
+        }
+
+        return a;
+      }
+    }
+  }
+  /* NOTREACHED */
+}
+
+static char *stbds_strdup(char *str)
+{
+  // to keep replaceable allocator simple, we don't want to use strdup.
+  // rolling our own also avoids problem of strdup vs _strdup
+  size_t len = strlen(str)+1;
+  char *p = (char*) STBDS_REALLOC(NULL, 0, len);
+  memmove(p, str, len);
+  return p;
+}
+
+#ifndef STBDS_STRING_ARENA_BLOCKSIZE_MIN
+#define STBDS_STRING_ARENA_BLOCKSIZE_MIN  512u
+#endif
+#ifndef STBDS_STRING_ARENA_BLOCKSIZE_MAX
+#define STBDS_STRING_ARENA_BLOCKSIZE_MAX  (1u<<20)
+#endif
+
+char *stbds_stralloc(stbds_string_arena *a, char *str)
+{
+  char *p;
+  size_t len = strlen(str)+1;
+  if (len > a->remaining) {
+    // compute the next blocksize
+    size_t blocksize = a->block;
+
+    // size is 512, 512, 1024, 1024, 2048, 2048, 4096, 4096, etc., so that
+    // there are log(SIZE) allocations to free when we destroy the table
+    blocksize = (size_t) (STBDS_STRING_ARENA_BLOCKSIZE_MIN) << (blocksize>>1);
+
+    // if size is under 1M, advance to next blocktype
+    if (blocksize < (size_t)(STBDS_STRING_ARENA_BLOCKSIZE_MAX))
+      ++a->block;
+
+    if (len > blocksize) {
+      // if string is larger than blocksize, then just allocate the full size.
+      // note that we still advance string_block so block size will continue
+      // increasing, so e.g. if somebody only calls this with 1000-long strings,
+      // eventually the arena will start doubling and handling those as well
+      stbds_string_block *sb = (stbds_string_block *) STBDS_REALLOC(NULL, 0, sizeof(*sb)-8 + len);
+      memmove(sb->storage, str, len);
+      if (a->storage) {
+        // insert it after the first element, so that we don't waste the space there
+        sb->next = a->storage->next;
+        a->storage->next = sb;
+      } else {
+        sb->next = 0;
+        a->storage = sb;
+        a->remaining = 0; // this is redundant, but good for clarity
+      }
+      return sb->storage;
+    } else {
+      stbds_string_block *sb = (stbds_string_block *) STBDS_REALLOC(NULL, 0, sizeof(*sb)-8 + blocksize);
+      sb->next = a->storage;
+      a->storage = sb;
+      a->remaining = blocksize;
+    }
+  }
+
+  STBDS_ASSERT(len <= a->remaining);
+  p = a->storage->storage + a->remaining - len;
+  a->remaining -= len;
+  memmove(p, str, len);
+  return p;
+}
+
+void stbds_strreset(stbds_string_arena *a)
+{
+  stbds_string_block *x,*y;
+  x = a->storage;
+  while (x) {
+    y = x->next;
+    STBDS_FREE(NULL, x);
+    x = y;
+  }
+  memset(a, 0, sizeof(*a));
+}
+
+#endif
+
+//////////////////////////////////////////////////////////////////////////////
+//
+//   UNIT TESTS
+//
+
+#ifdef STBDS_UNIT_TESTS
+#include <stdio.h>
+#ifdef STBDS_ASSERT_WAS_UNDEFINED
+#undef STBDS_ASSERT
+#endif
+#ifndef STBDS_ASSERT
+#define STBDS_ASSERT assert
+#include <assert.h>
+#endif
+
+typedef struct { int key,b,c,d; } stbds_struct;
+typedef struct { int key[2],b,c,d; } stbds_struct2;
+
+static char buffer[256];
+char *strkey(int n)
+{
+#if defined(_WIN32) && defined(__STDC_WANT_SECURE_LIB__)
+   sprintf_s(buffer, sizeof(buffer), "test_%d", n);
+#else
+   sprintf(buffer, "test_%d", n);
+#endif
+   return buffer;
+}
+
+void stbds_unit_tests(void)
+{
+#if defined(_MSC_VER) && _MSC_VER <= 1200 && defined(__cplusplus)
+  // VC6 C++ doesn't like the template<> trick on unnamed structures, so do nothing!
+  STBDS_ASSERT(0);
+#else
+  const int testsize = 100000;
+  const int testsize2 = testsize/20;
+  int *arr=NULL;
+  struct { int   key;        int value; }  *intmap  = NULL;
+  struct { char *key;        int value; }  *strmap  = NULL, s;
+  struct { stbds_struct key; int value; }  *map     = NULL;
+  stbds_struct                             *map2    = NULL;
+  stbds_struct2                            *map3    = NULL;
+  stbds_string_arena                        sa      = { 0 };
+  int key3[2] = { 1,2 };
+  ptrdiff_t temp;
+
+  int i,j;
+
+  STBDS_ASSERT(arrlen(arr)==0);
+  for (i=0; i < 20000; i += 50) {
+    for (j=0; j < i; ++j)
+      arrpush(arr,j);
+    arrfree(arr);
+  }
+
+  for (i=0; i < 4; ++i) {
+    arrpush(arr,1); arrpush(arr,2); arrpush(arr,3); arrpush(arr,4);
+    arrdel(arr,i);
+    arrfree(arr);
+    arrpush(arr,1); arrpush(arr,2); arrpush(arr,3); arrpush(arr,4);
+    arrdelswap(arr,i);
+    arrfree(arr);
+  }
+
+  for (i=0; i < 5; ++i) {
+    arrpush(arr,1); arrpush(arr,2); arrpush(arr,3); arrpush(arr,4);
+    stbds_arrins(arr,i,5);
+    STBDS_ASSERT(arr[i] == 5);
+    if (i < 4)
+      STBDS_ASSERT(arr[4] == 4);
+    arrfree(arr);
+  }
+
+  i = 1;
+  STBDS_ASSERT(hmgeti(intmap,i) == -1);
+  hmdefault(intmap, -2);
+  STBDS_ASSERT(hmgeti(intmap, i) == -1);
+  STBDS_ASSERT(hmget (intmap, i) == -2);
+  for (i=0; i < testsize; i+=2)
+    hmput(intmap, i, i*5);
+  for (i=0; i < testsize; i+=1) {
+    if (i & 1) STBDS_ASSERT(hmget(intmap, i) == -2 );
+    else       STBDS_ASSERT(hmget(intmap, i) == i*5);
+    if (i & 1) STBDS_ASSERT(hmget_ts(intmap, i, temp) == -2 );
+    else       STBDS_ASSERT(hmget_ts(intmap, i, temp) == i*5);
+  }
+  for (i=0; i < testsize; i+=2)
+    hmput(intmap, i, i*3);
+  for (i=0; i < testsize; i+=1)
+    if (i & 1) STBDS_ASSERT(hmget(intmap, i) == -2 );
+    else       STBDS_ASSERT(hmget(intmap, i) == i*3);
+  for (i=2; i < testsize; i+=4)
+    hmdel(intmap, i); // delete half the entries
+  for (i=0; i < testsize; i+=1)
+    if (i & 3) STBDS_ASSERT(hmget(intmap, i) == -2 );
+    else       STBDS_ASSERT(hmget(intmap, i) == i*3);
+  for (i=0; i < testsize; i+=1)
+    hmdel(intmap, i); // delete the rest of the entries
+  for (i=0; i < testsize; i+=1)
+    STBDS_ASSERT(hmget(intmap, i) == -2 );
+  hmfree(intmap);
+  for (i=0; i < testsize; i+=2)
+    hmput(intmap, i, i*3);
+  hmfree(intmap);
+
+  #if defined(__clang__) || defined(__GNUC__)
+  #ifndef __cplusplus
+  intmap = NULL;
+  hmput(intmap, 15, 7);
+  hmput(intmap, 11, 3);
+  hmput(intmap,  9, 5);
+  STBDS_ASSERT(hmget(intmap, 9) == 5);
+  STBDS_ASSERT(hmget(intmap, 11) == 3);
+  STBDS_ASSERT(hmget(intmap, 15) == 7);
+  #endif
+  #endif
+
+  for (i=0; i < testsize; ++i)
+    stralloc(&sa, strkey(i));
+  strreset(&sa);
+
+  {
+    s.key = "a", s.value = 1;
+    shputs(strmap, s);
+    STBDS_ASSERT(*strmap[0].key == 'a');
+    STBDS_ASSERT(strmap[0].key == s.key);
+    STBDS_ASSERT(strmap[0].value == s.value);
+    shfree(strmap);
+  }
+
+  {
+    s.key = "a", s.value = 1;
+    sh_new_strdup(strmap);
+    shputs(strmap, s);
+    STBDS_ASSERT(*strmap[0].key == 'a');
+    STBDS_ASSERT(strmap[0].key != s.key);
+    STBDS_ASSERT(strmap[0].value == s.value);
+    shfree(strmap);
+  }
+
+  {
+    s.key = "a", s.value = 1;
+    sh_new_arena(strmap);
+    shputs(strmap, s);
+    STBDS_ASSERT(*strmap[0].key == 'a');
+    STBDS_ASSERT(strmap[0].key != s.key);
+    STBDS_ASSERT(strmap[0].value == s.value);
+    shfree(strmap);
+  }
+
+  for (j=0; j < 2; ++j) {
+    STBDS_ASSERT(shgeti(strmap,"foo") == -1);
+    if (j == 0)
+      sh_new_strdup(strmap);
+    else
+      sh_new_arena(strmap);
+    STBDS_ASSERT(shgeti(strmap,"foo") == -1);
+    shdefault(strmap, -2);
+    STBDS_ASSERT(shgeti(strmap,"foo") == -1);
+    for (i=0; i < testsize; i+=2)
+      shput(strmap, strkey(i), i*3);
+    for (i=0; i < testsize; i+=1)
+      if (i & 1) STBDS_ASSERT(shget(strmap, strkey(i)) == -2 );
+      else       STBDS_ASSERT(shget(strmap, strkey(i)) == i*3);
+    for (i=2; i < testsize; i+=4)
+      shdel(strmap, strkey(i)); // delete half the entries
+    for (i=0; i < testsize; i+=1)
+      if (i & 3) STBDS_ASSERT(shget(strmap, strkey(i)) == -2 );
+      else       STBDS_ASSERT(shget(strmap, strkey(i)) == i*3);
+    for (i=0; i < testsize; i+=1)
+      shdel(strmap, strkey(i)); // delete the rest of the entries
+    for (i=0; i < testsize; i+=1)
+      STBDS_ASSERT(shget(strmap, strkey(i)) == -2 );
+    shfree(strmap);
+  }
+
+  {
+    struct { char *key; char value; } *hash = NULL;
+    char name[4] = "jen";
+    shput(hash, "bob"   , 'h');
+    shput(hash, "sally" , 'e');
+    shput(hash, "fred"  , 'l');
+    shput(hash, "jen"   , 'x');
+    shput(hash, "doug"  , 'o');
+
+    shput(hash, name    , 'l');
+    shfree(hash);
+  }
+
+  for (i=0; i < testsize; i += 2) {
+    stbds_struct s = { i,i*2,i*3,i*4 };
+    hmput(map, s, i*5);
+  }
+
+  for (i=0; i < testsize; i += 1) {
+    stbds_struct s = { i,i*2,i*3  ,i*4 };
+    stbds_struct t = { i,i*2,i*3+1,i*4 };
+    if (i & 1) STBDS_ASSERT(hmget(map, s) == 0);
+    else       STBDS_ASSERT(hmget(map, s) == i*5);
+    if (i & 1) STBDS_ASSERT(hmget_ts(map, s, temp) == 0);
+    else       STBDS_ASSERT(hmget_ts(map, s, temp) == i*5);
+    //STBDS_ASSERT(hmget(map, t.key) == 0);
+  }
+
+  for (i=0; i < testsize; i += 2) {
+    stbds_struct s = { i,i*2,i*3,i*4 };
+    hmputs(map2, s);
+  }
+  hmfree(map);
+
+  for (i=0; i < testsize; i += 1) {
+    stbds_struct s = { i,i*2,i*3,i*4 };
+    stbds_struct t = { i,i*2,i*3+1,i*4 };
+    if (i & 1) STBDS_ASSERT(hmgets(map2, s.key).d == 0);
+    else       STBDS_ASSERT(hmgets(map2, s.key).d == i*4);
+    //STBDS_ASSERT(hmgetp(map2, t.key) == 0);
+  }
+  hmfree(map2);
+
+  for (i=0; i < testsize; i += 2) {
+    stbds_struct2 s = { { i,i*2 }, i*3,i*4, i*5 };
+    hmputs(map3, s);
+  }
+  for (i=0; i < testsize; i += 1) {
+    stbds_struct2 s = { { i,i*2}, i*3, i*4, i*5 };
+    stbds_struct2 t = { { i,i*2}, i*3+1, i*4, i*5 };
+    if (i & 1) STBDS_ASSERT(hmgets(map3, s.key).d == 0);
+    else       STBDS_ASSERT(hmgets(map3, s.key).d == i*5);
+    //STBDS_ASSERT(hmgetp(map3, t.key) == 0);
+  }
+#endif
+}
+#endif
+
+
+/*
+------------------------------------------------------------------------------
+This software is available under 2 licenses -- choose whichever you prefer.
+------------------------------------------------------------------------------
+ALTERNATIVE A - MIT License
+Copyright (c) 2019 Sean Barrett
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+------------------------------------------------------------------------------
+ALTERNATIVE B - Public Domain (www.unlicense.org)
+This is free and unencumbered software released into the public domain.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+software, either in source code form or as a compiled binary, for any purpose,
+commercial or non-commercial, and by any means.
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and to
+the detriment of our heirs and successors. We intend this dedication to be an
+overt act of relinquishment in perpetuity of all present and future rights to
+this software under copyright law.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+------------------------------------------------------------------------------
+*/
diff --git a/Makefile b/Makefile
index 46e938c..f50b43d 100644
--- a/Makefile
+++ b/Makefile
@@ -6,6 +6,7 @@ FLEX ?= flex
 
 SRC_DIR := src
 INC_DIR := include
+TEST_DIR := test
 BUILD_DIR := build
 
 PARSER_Y := $(SRC_DIR)/parser.y
@@ -23,11 +24,12 @@ LEXER_O := $(BUILD_DIR)/lex.yy.o
 OBJS := $(C_OBJS) $(PARSER_O) $(LEXER_O)
 
 TARGET := $(BUILD_DIR)/imp
+TEST_TARGET := $(BUILD_DIR)/test
 
-CFLAGS += -I$(INC_DIR) -MMD -MP
+CFLAGS += -I$(INC_DIR) -I. -MMD -MP
 DEPS := $(OBJS:.o=.d)
 
-.PHONY: all clean example repl
+.PHONY: all clean example repl test
 
 all: $(TARGET)
 
@@ -52,12 +54,18 @@ $(LEXER_C): $(LEXER_L) $(PARSER_H) | $(BUILD_DIR)
 $(LEXER_O): $(LEXER_C)
 	$(CC) $(CFLAGS) -c $< -o $@
 
+$(TEST_TARGET): $(wildcard $(TEST_DIR)/*.c) $(filter-out $(BUILD_DIR)/main.o, $(OBJS)) | $(BUILD_DIR)
+	$(CC) $(CFLAGS) $^ -o $@ $(LDFLAGS)
+
 example: $(TARGET)
 	./$(TARGET) -i examples/example.imp
 
 repl: $(TARGET)
 	./$(TARGET)
 
+test: $(BUILD_DIR)/test
+	./$(BUILD_DIR)/test
+
 clean:
 	@rm -rf $(BUILD_DIR)
 
diff --git a/include/ast.h b/include/ast.h
index 068372e..a687a9b 100644
--- a/include/ast.h
+++ b/include/ast.h
@@ -8,7 +8,6 @@
  * Provides data structures, enums, and functions for creating, managing, cloning, and freeing AST nodes.
  *
  * @author Flavian Kaufmann
- * @date 2025-05-23
  */
 
 
@@ -142,7 +141,7 @@ IMP_ASTNode *imp_ast_clone(const IMP_ASTNode *node);
  *
  * @param node Node to free.
  */
-void imp_ast_free(IMP_ASTNode *node);
+void imp_ast_destroy(IMP_ASTNode *node);
 
 /**
  * Creates a new linked list of AST nodes.
@@ -160,6 +159,6 @@ IMP_ASTNodeList *imp_ast_list(IMP_ASTNode *node, IMP_ASTNodeList *list);
  *
  * @param list List to free.
  */
-void imp_ast_list_free(IMP_ASTNodeList *list);
+void imp_ast_list_destroy(IMP_ASTNodeList *list);
 
 #endif /* IMP_AST_H */
\ No newline at end of file
diff --git a/include/driver.h b/include/driver.h
new file mode 100644
index 0000000..40cfc58
--- /dev/null
+++ b/include/driver.h
@@ -0,0 +1,13 @@
+#ifndef IMP_DRIVER_H
+#define IMP_DRIVER_H
+
+#include "interpreter_context.h"
+
+int imp_driver_interpret_file (IMP_InterpreterContext *context, const char *path);
+int imp_driver_interpret_str (IMP_InterpreterContext *context, const char *str);
+int imp_driver_print_ast_file (const char *path);
+
+void imp_driver_print_var_table(IMP_InterpreterContext *context);
+void imp_driver_print_proc_table(IMP_InterpreterContext *context);
+
+#endif /* IMP_DRIVER_H */
\ No newline at end of file
diff --git a/include/hashmap.h b/include/hashmap.h
deleted file mode 100644
index 7cc20b1..0000000
--- a/include/hashmap.h
+++ /dev/null
@@ -1,63 +0,0 @@
-#ifndef HASHMAP_H
-#define HASHMAP_H
-
-/* Hashmap Handle */
-typedef struct HashMap *hashmap_t;
-
-/* Hashmap Key Iterator Handle */
-typedef struct HashMapKeysIter *hashmap_keys_iter_t;
-
-
-/* 
-  Creates hashmap that maps char* to void*.
-    Keys are copied, and will be freed when the hashmap is freed.
-    Elements are not copied, and must be freed by the caller.
-    Caller is responsible for freeing the hashmap using hashmap_free.
-*/
-hashmap_t hashmap_create(void);
-
-/*
-  Frees the hashmap and all keys.
-    Elements are not freed, and must be freed by the caller.
-*/
-void hashmap_free(hashmap_t map);
-
-/* 
-  Looks up element with given key.
-    Returns pointer to element, or NULL if not found.
-*/
-void **hashmap_get(hashmap_t map, const char *key);
-
-/* 
-  Inserts element with given key.
-    If key already exists, the old element is replaced (caller is responsible for freeing beforehand).
-*/
-void hashmap_insert(hashmap_t map, const char *key, void *element);
-
-/* 
-  Deletes element with given key.
-    Caller is responsible for freeing the element.
-    Returns 0 on success, -1 when not found.
-*/
-int hashmap_delete(hashmap_t map, const char *key);
-
-
-/* 
-  Creates iterator for keys.
-    Caller is responsible for freeing the iterator using hashmap_keys_iter_free.
-    Iterator is invalid when the hashmap is modified and must be freed.
-*/
-hashmap_keys_iter_t hashmap_keys_iter_create(hashmap_t map);
-
-/* 
-  Returns next key in the iterator.
-    Returns NULL when there are no more keys.
-    Keys are not copied, and must not be freed.
-*/
-const char *hashmap_keys_iter_next(hashmap_keys_iter_t iter);
-
-/* Frees the iterator. */
-void hashmap_keys_iter_free(hashmap_keys_iter_t iter);
-
-
-#endif
\ No newline at end of file
diff --git a/include/interpreter.h b/include/interpreter.h
index 5eff23f..d5a1e7a 100644
--- a/include/interpreter.h
+++ b/include/interpreter.h
@@ -1,26 +1,30 @@
-#ifndef INTERPRETER_H
-#define INTERPRETER_H
+#ifndef IMP_INTERPRETER_H
+#define IMP_INTERPRETER_H
 
 
-#include "ast.h"
-
+/**
+ * @file interpreter.h
+ * @brief Interpreter for evaluating IMP language programs.
+ *
+ * @author Flavian Kaufmann
+ */
 
-typedef struct Context *context_t;
 
+#include "ast.h"
+#include "interpreter_context.h"
 
-context_t context_create(void);
-void context_free(context_t context);
-
-int context_get_var(context_t context, const char *name);
-void context_set_var(context_t context, const char *name, int value);
-void context_print_var_table(context_t context);
-void context_print_proc_table(context_t context);
 
-int interp_ast(context_t context, IMP_ASTNode *node);
-int interp_file (context_t context, const char *path);
-int interp_str (context_t context, const char *str);
+/**
+ * Evaluates an AST node within a given context.
+ *
+ * @param context The interpreter context.
+ * @param node AST node to evaluate.
+ * @return Status code or result of evaluation. (0 for success, non-zero for error).
+ *
+ * @note The interpreter does neither take ownership of the context nor the AST node.
+ */
+int imp_interpreter_interpret_ast(IMP_InterpreterContext *context, const IMP_ASTNode *node);
 
-int print_ast_file (const char *path);
 
 
-#endif
\ No newline at end of file
+#endif /* IMP_INTERPRETER_H */
\ No newline at end of file
diff --git a/include/interpreter_context.h b/include/interpreter_context.h
new file mode 100644
index 0000000..acc63c1
--- /dev/null
+++ b/include/interpreter_context.h
@@ -0,0 +1,143 @@
+#ifndef IMP_INTERPRETER_CONTEXT_H
+#define IMP_INTERPRETER_CONTEXT_H
+
+/**
+ * @file interpreter_context.h
+ * @brief Defines the context structure for the IMP interpreter.
+ *
+ * Provides the interface for managing the interpreter state, specifically
+ * the variable and procedure environments.
+ *
+ * Author: Flavian Kaufmann
+ */
+
+#include "ast.h"
+
+/**
+ * @brief Opaque type representing the interpreter context.
+ */
+typedef struct IMP_InterpreterContext IMP_InterpreterContext;
+
+/**
+ * @brief Opaque type for iterating over variable entries in the context.
+ */
+typedef struct IMP_InterpreterContextVarIter IMP_InterpreterContextVarIter;
+
+/**
+ * @brief Opaque type for iterating over procedure entries in the context.
+ */
+typedef struct IMP_InterpreterContextProcIter IMP_InterpreterContextProcIter;
+
+/**
+ * @brief A single variable entry in the interpreter's environment.
+ */
+typedef struct IMP_InterpreterContextVarTableEntry {
+  const char *key;  /**< The variable name (identifier). */
+  int value;        /**< The value associated with the variable. */
+} IMP_InterpreterContextVarTableEntry;
+
+/**
+ * @brief A single procedure entry in the interpreter's environment.
+ */
+typedef struct IMP_InterpreterContextProcTableEntry {
+  const char *key;             /**< The procedure name (identifier). */
+  const IMP_ASTNode *value;    /**< The AST node representing the procedure declaration. */
+} IMP_InterpreterContextProcTableEntry;
+
+/**
+ * @brief Creates and initializes a new interpreter context.
+ * 
+ * @return A pointer to the newly created context.
+ */
+IMP_InterpreterContext *imp_interpreter_context_create(void);
+
+/**
+ * @brief Frees all memory associated with the interpreter context.
+ * 
+ * @param context The context to destroy.
+ */
+void imp_interpreter_context_destroy(IMP_InterpreterContext *context);
+
+/**
+ * @brief Retrieves the value of a variable from the context.
+ * 
+ * @param context The interpreter context.
+ * @param name The name of the variable. (Is copied internally.)
+ * @return The value of the variable. Returns 0 if the variable is not found.
+ */
+int imp_interpreter_context_var_get(IMP_InterpreterContext *context, const char *name);
+
+/**
+ * @brief Sets or updates the value of a variable in the context.
+ * 
+ * @param context The interpreter context.
+ * @param name The name of the variable. (Is copied internally.)
+ * @param value The value to assign. (If value is 0, the variable is removed from the context.)
+ */
+void imp_interpreter_context_var_set(IMP_InterpreterContext *context, const char *name, int value);
+
+/**
+ * @brief Retrieves the AST node for a procedure from the context.
+ * 
+ * @param context The interpreter context.
+ * @param name The name of the procedure. (Is copied internally.)
+ * @return A pointer to the procedure's AST node, or NULL if not found.
+ */
+const IMP_ASTNode *imp_interpreter_context_proc_get(IMP_InterpreterContext *context, const char *name);
+
+/**
+ * @brief Adds or updates a procedure in the context.
+ * 
+ * @param context The interpreter context.
+ * @param name The name of the procedure. (Is copied internally.)
+ * @param proc The AST node representing the procedure body. (Is cloned internally.)
+ */
+void imp_interpreter_context_proc_set(IMP_InterpreterContext *context, const char *name, const IMP_ASTNode *proc);
+
+/**
+ * @brief Creates an iterator over the variables in the context. (Is invalid if the variable table is modified.)
+ * 
+ * @param context The interpreter context.
+ * @return A pointer to the variable iterator.
+ */
+IMP_InterpreterContextVarIter *imp_interpreter_context_var_iter_create(IMP_InterpreterContext *context);
+
+/**
+ * @brief Destroys a variable iterator.
+ * 
+ * @param iter The iterator to destroy.
+ */
+void imp_interpreter_context_var_iter_destroy(IMP_InterpreterContextVarIter *iter);
+
+/**
+ * @brief Retrieves the next variable entry from the iterator.
+ * 
+ * @param iter The variable iterator.
+ * @return A pointer to the next variable entry, or NULL if end is reached.
+ */
+IMP_InterpreterContextVarTableEntry *imp_interpreter_context_var_iter_next(IMP_InterpreterContextVarIter *iter);
+
+/**
+ * @brief Creates an iterator over the procedures in the context. (Is invalid if the procedure table is modified.)
+ * 
+ * @param context The interpreter context.
+ * @return A pointer to the procedure iterator.
+ */
+IMP_InterpreterContextProcIter *imp_interpreter_context_proc_iter_create(IMP_InterpreterContext *context);
+
+/**
+ * @brief Destroys a procedure iterator.
+ * 
+ * @param iter The iterator to destroy.
+ */
+void imp_interpreter_context_proc_iter_destroy(IMP_InterpreterContextProcIter *iter);
+
+/**
+ * @brief Retrieves the next procedure entry from the iterator.
+ * 
+ * @param iter The procedure iterator.
+ * @return A pointer to the next procedure entry, or NULL if end is reached.
+ */
+IMP_InterpreterContextProcTableEntry *imp_interpreter_context_proc_iter_next(IMP_InterpreterContextProcIter *iter);
+
+#endif /* IMP_INTERPRETER_CONTEXT_H */
\ No newline at end of file
diff --git a/include/repl.h b/include/repl.h
index 4b833ad..5e6e168 100644
--- a/include/repl.h
+++ b/include/repl.h
@@ -1,8 +1,8 @@
-#ifndef REPL_H
-#define REPL_H
+#ifndef IMP_REPL_H
+#define IMP_REPL_H
 
 
-void repl(void);
+void imp_repl(void);
 
 
-#endif
\ No newline at end of file
+#endif /* IMP_REPL_H */
\ No newline at end of file
diff --git a/src/ast.c b/src/ast.c
index 03e6100..9c13d79 100644
--- a/src/ast.c
+++ b/src/ast.c
@@ -170,27 +170,27 @@ IMP_ASTNode *imp_ast_clone(const IMP_ASTNode *node) {
   }
 }
 
-void imp_ast_free(IMP_ASTNode *node) {
+void imp_ast_destroy(IMP_ASTNode *node) {
   if (!node) return;
   switch (node->type) {
     case IMP_AST_NT_SKIP:
       break;
     case IMP_AST_NT_ASSIGN:
-      imp_ast_free(node->data.assign.var);
-      imp_ast_free(node->data.assign.aexpr);
+      imp_ast_destroy(node->data.assign.var);
+      imp_ast_destroy(node->data.assign.aexpr);
       break;
     case IMP_AST_NT_SEQ:
-      imp_ast_free(node->data.seq.fst_stmt);
-      imp_ast_free(node->data.seq.snd_stmt);
+      imp_ast_destroy(node->data.seq.fst_stmt);
+      imp_ast_destroy(node->data.seq.snd_stmt);
       break;
     case IMP_AST_NT_IF:
-      imp_ast_free(node->data.if_stmt.cond_bexpr);
-      imp_ast_free(node->data.if_stmt.then_stmt);
-      imp_ast_free(node->data.if_stmt.else_stmt);
+      imp_ast_destroy(node->data.if_stmt.cond_bexpr);
+      imp_ast_destroy(node->data.if_stmt.then_stmt);
+      imp_ast_destroy(node->data.if_stmt.else_stmt);
       break;
     case IMP_AST_NT_WHILE:
-      imp_ast_free(node->data.while_stmt.cond_bexpr);
-      imp_ast_free(node->data.while_stmt.body_stmt);
+      imp_ast_destroy(node->data.while_stmt.cond_bexpr);
+      imp_ast_destroy(node->data.while_stmt.body_stmt);
       break;
     case IMP_AST_NT_INT:
       break;
@@ -198,35 +198,35 @@ void imp_ast_free(IMP_ASTNode *node) {
       free(node->data.variable.name);
       break;
     case IMP_AST_NT_AOP:
-      imp_ast_free(node->data.arith_op.l_aexpr);
-      imp_ast_free(node->data.arith_op.r_aexpr);
+      imp_ast_destroy(node->data.arith_op.l_aexpr);
+      imp_ast_destroy(node->data.arith_op.r_aexpr);
       break;
     case IMP_AST_NT_BOP:
-      imp_ast_free(node->data.bool_op.l_bexpr);
-      imp_ast_free(node->data.bool_op.r_bexpr);
+      imp_ast_destroy(node->data.bool_op.l_bexpr);
+      imp_ast_destroy(node->data.bool_op.r_bexpr);
       break;
     case IMP_AST_NT_ROP:
-      imp_ast_free(node->data.rel_op.l_aexpr);
-      imp_ast_free(node->data.rel_op.r_aexpr);
+      imp_ast_destroy(node->data.rel_op.l_aexpr);
+      imp_ast_destroy(node->data.rel_op.r_aexpr);
       break;
     case IMP_AST_NT_NOT:
-      imp_ast_free(node->data.bool_not.bexpr);
+      imp_ast_destroy(node->data.bool_not.bexpr);
       break;
     case IMP_AST_NT_LET:
-      imp_ast_free(node->data.let_stmt.var);
-      imp_ast_free(node->data.let_stmt.aexpr);
-      imp_ast_free(node->data.let_stmt.body_stmt);
+      imp_ast_destroy(node->data.let_stmt.var);
+      imp_ast_destroy(node->data.let_stmt.aexpr);
+      imp_ast_destroy(node->data.let_stmt.body_stmt);
       break;
     case IMP_AST_NT_PROCDECL:
       free(node->data.proc_decl.name);
-      imp_ast_list_free(node->data.proc_decl.val_args);
-      imp_ast_list_free(node->data.proc_decl.var_args);
-      imp_ast_free(node->data.proc_decl.body_stmt);
+      imp_ast_list_destroy(node->data.proc_decl.val_args);
+      imp_ast_list_destroy(node->data.proc_decl.var_args);
+      imp_ast_destroy(node->data.proc_decl.body_stmt);
       break;
     case IMP_AST_NT_PROCCALL:
       free(node->data.proc_call.name);
-      imp_ast_list_free(node->data.proc_call.val_args);
-      imp_ast_list_free(node->data.proc_call.var_args);
+      imp_ast_list_destroy(node->data.proc_call.val_args);
+      imp_ast_list_destroy(node->data.proc_call.var_args);
       break;
     default: assert(0 && "Unknown AST node type");
   }
@@ -241,9 +241,9 @@ IMP_ASTNodeList *imp_ast_list(IMP_ASTNode *node, IMP_ASTNodeList *list) {
   return new_list;
 }
 
-void imp_ast_list_free(IMP_ASTNodeList *list) {
+void imp_ast_list_destroy(IMP_ASTNodeList *list) {
   if (!list) return;
-  imp_ast_free(list->node);
-  imp_ast_list_free(list->next);
+  imp_ast_destroy(list->node);
+  imp_ast_list_destroy(list->next);
   free(list);
 }
\ No newline at end of file
diff --git a/src/driver.c b/src/driver.c
index 441ee40..5f6037d 100644
--- a/src/driver.c
+++ b/src/driver.c
@@ -1,44 +1,238 @@
-#include <stdio.h>
+#include "driver.h"
+
 #include <stdlib.h>
-#include <string.h>
-#include <unistd.h>
+#include <stdio.h>
+#include <assert.h>
 
+#include "ast.h"
 #include "interpreter.h"
-#include "repl.h"
 
 
-static int interpret_file(const char *path) {
-  context_t context = context_create();
-  if (interp_file(context, path)) {
-    fprintf(stderr, "Error interpreting file: %s\n", path);
-    context_free(context);
+typedef void *YY_BUFFER_STATE;
+extern FILE *yyin;
+extern IMP_ASTNode *ast_root;
+extern int yyparse(void);
+extern void yyrestart (FILE*);
+extern YY_BUFFER_STATE yy_scan_string(const char*);
+extern void yy_delete_buffer(YY_BUFFER_STATE);
+
+int imp_driver_interpret_file (IMP_InterpreterContext *context, const char *path) {
+  yyin = fopen(path, "r");
+  if (!yyin) return -1;
+  yyrestart(yyin);
+  if (yyparse()) {
+    imp_ast_destroy(ast_root);
+    fclose(yyin);
+    return -1;
+  }
+  if (imp_interpreter_interpret_ast(context, ast_root)) {
+    imp_ast_destroy(ast_root);
+    fclose(yyin);
     return -1;
   }
-  context_print_var_table(context);
-  context_free(context);
+  imp_ast_destroy(ast_root);
+  fclose(yyin);
   return 0;
 }
 
-int main(int argc, char **argv) {
-  int opt;
-  while ((opt = getopt(argc, argv, "i:a:h")) != -1) {
-    switch (opt) {
-    case 'i': 
-      return interpret_file(optarg) ? EXIT_FAILURE : EXIT_SUCCESS;
-    case 'a':
-      return print_ast_file(optarg) ? EXIT_FAILURE : EXIT_SUCCESS;
-    case 'h':
-    default:
-      fprintf(stderr, 
-        "Usage: %s [ARGS]\n"
-        "  (no args)          start REPL\n"
-        "  -i <program.imp>   interpret program\n"
-        "  -a <program.imp>   print ast\n"
-        "  -h                 print this message\n",
-        argv[0]);
-      return (opt == 'h') ? EXIT_SUCCESS : EXIT_FAILURE;
-    }
-  }
-  repl();
-  return EXIT_SUCCESS;
+int imp_driver_interpret_str (IMP_InterpreterContext *context, const char *str) {
+  YY_BUFFER_STATE buf = yy_scan_string(str);
+  if (yyparse()) {
+    imp_ast_destroy(ast_root);
+    yy_delete_buffer(buf);
+    return -1;
+  }
+  if (imp_interpreter_interpret_ast(context, ast_root)) {
+    imp_ast_destroy(ast_root);
+    yy_delete_buffer(buf);
+    return -1;
+  }
+  yy_delete_buffer(buf);
+  return 0;
+}
+
+static void ast_print (IMP_ASTNode *node, int depth) {
+  int indent = depth * 2;
+  switch (node->type) {
+    case IMP_AST_NT_SKIP: {
+      printf("%*sSKIP\n", indent, "");
+      break;
+    }
+    case IMP_AST_NT_ASSIGN: {
+      printf("%*sASSIGN %s=", indent, "", 
+             node->data.assign.var->data.variable.name);
+      ast_print(node->data.assign.aexpr, 0);
+      printf("\n");
+      break;
+    }
+    case IMP_AST_NT_SEQ: {
+      ast_print(node->data.seq.fst_stmt, depth);
+      printf("%*sSEQ\n", indent, "");
+      ast_print(node->data.seq.snd_stmt, depth);
+      break;
+    }
+    case IMP_AST_NT_IF: {
+      printf("%*sIF (", indent, "");
+      ast_print(node->data.if_stmt.cond_bexpr, 0);
+      printf(")\n");
+      ast_print(node->data.if_stmt.then_stmt, depth + 1);
+      printf("%*sELSE\n", indent, "");
+      ast_print(node->data.if_stmt.else_stmt, depth + 1);
+      break;
+    }
+    case IMP_AST_NT_WHILE: {
+      printf("%*sWHILE (", indent, "");
+      ast_print(node->data.while_stmt.cond_bexpr, 0);
+      printf(")\n");
+      ast_print(node->data.while_stmt.body_stmt, depth + 1);
+      break;
+    }
+    case IMP_AST_NT_INT: {
+      printf("%d", node->data.integer.val);
+      break;
+    }
+    case IMP_AST_NT_VAR: {
+      printf("%s", node->data.variable.name);
+      break;
+    }
+    case IMP_AST_NT_AOP: {
+      printf("(");
+      ast_print(node->data.arith_op.l_aexpr, 0);
+      switch (node->data.arith_op.aopr) {
+        case IMP_AST_AOP_ADD: printf(" + "); break;
+        case IMP_AST_AOP_SUB: printf(" - "); break;
+        case IMP_AST_AOP_MUL: printf(" * "); break;
+        default: assert(0);
+      }
+      ast_print(node->data.arith_op.r_aexpr, 0);
+      printf(")");
+      break;
+    }
+    case IMP_AST_NT_BOP: {
+      printf("(");
+      ast_print(node->data.bool_op.l_bexpr, 0);
+      switch (node->data.bool_op.bopr) {
+        case IMP_AST_BOP_AND: printf(" && "); break;
+        case IMP_AST_BOP_OR:  printf(" || "); break;
+        default: assert(0);
+      }
+      ast_print(node->data.bool_op.r_bexpr, 0);
+      printf(")");
+      break;
+    }
+    case IMP_AST_NT_NOT: {
+      printf("!");
+      ast_print(node->data.bool_not.bexpr, 0);
+      break;
+    }
+    case IMP_AST_NT_ROP: {
+      printf("(");
+      ast_print(node->data.rel_op.l_aexpr, 0);
+      switch (node->data.rel_op.ropr) {
+        case IMP_AST_ROP_EQ: printf(" == "); break;
+        case IMP_AST_ROP_NE: printf(" != "); break;
+        case IMP_AST_ROP_LT: printf(" < "); break;
+        case IMP_AST_ROP_LE: printf(" <= "); break;
+        case IMP_AST_ROP_GT: printf(" > "); break;
+        case IMP_AST_ROP_GE: printf(" >= "); break;
+        default: assert(0);
+      }
+      ast_print(node->data.rel_op.r_aexpr, 0);
+      printf(")");
+      break;
+    }
+    case IMP_AST_NT_LET: {
+      printf("%*sLET %s = ", indent, "", node->data.let_stmt.var->data.variable.name);
+      ast_print(node->data.let_stmt.aexpr, 0);
+      printf("\n");
+      ast_print(node->data.let_stmt.body_stmt, depth + 1);
+      break;
+    }
+    case IMP_AST_NT_PROCDECL: {
+      printf("%*sPROC %s(", indent, "", node->data.proc_decl.name);
+      IMP_ASTNodeList *args = node->data.proc_decl.val_args;
+      while (args) {
+        printf("%s", args->node->data.variable.name);
+        args = args->next;
+        if (args) printf(", ");
+      }
+      printf("; ");
+      IMP_ASTNodeList *vargs = node->data.proc_decl.var_args;
+      while (vargs) {
+        printf("%s", vargs->node->data.variable.name);
+        vargs = vargs->next;
+        if (vargs) printf(", ");
+      }
+      printf(")\n");
+      ast_print(node->data.proc_decl.body_stmt, depth + 1);
+      break;
+    }
+    case IMP_AST_NT_PROCCALL: {
+      printf("%*sCALL %s(", indent, "", node->data.proc_call.name);
+      IMP_ASTNodeList *args = node->data.proc_call.val_args;
+      while (args) {
+        printf("%s", args->node->data.variable.name);
+        args = args->next;
+        if (args) printf(", ");
+      }
+      printf("; ");
+      IMP_ASTNodeList *vargs = node->data.proc_call.var_args;
+      while (vargs) {
+        printf("%s", vargs->node->data.variable.name);
+        vargs = vargs->next;
+        if (vargs) printf(", ");
+      }
+      printf(")\n");
+      break;
+    }
+    default: assert(0);
+  }
+}
+
+int imp_driver_print_ast_file (const char *path) {
+  yyin = fopen(path, "r");
+  if (!yyin) return -1;
+  yyrestart(yyin);
+  if (yyparse()) {
+    imp_ast_destroy(ast_root);
+    fclose(yyin);
+    return -1;
+  }
+  ast_print(ast_root, 0);
+  imp_ast_destroy(ast_root);
+  fclose(yyin);
+  return 0;
+}
+
+void imp_driver_print_var_table(IMP_InterpreterContext *context) {
+  IMP_InterpreterContextVarIter *iter = imp_interpreter_context_var_iter_create(context);
+  const IMP_InterpreterContextVarTableEntry *var_entry;
+  while ((var_entry = imp_interpreter_context_var_iter_next(iter))) {
+    printf("%s = %d\n", var_entry->key, var_entry->value);
+  }
+  imp_interpreter_context_var_iter_destroy(iter);
+}
+
+void imp_driver_print_proc_table(IMP_InterpreterContext *context) {
+  IMP_InterpreterContextProcIter *iter = imp_interpreter_context_proc_iter_create(context);
+  const IMP_InterpreterContextProcTableEntry *proc_entry;
+  while ((proc_entry = imp_interpreter_context_proc_iter_next(iter))) {
+    const IMP_ASTNode *procdecl = proc_entry->value;
+    printf("%s(", proc_entry->key);
+    IMP_ASTNodeList *args = procdecl->data.proc_decl.val_args;
+    while (args) {
+      printf("%s", args->node->data.variable.name);
+      args = args->next;
+      if (args) printf(", ");
+    }
+    printf("; ");
+    IMP_ASTNodeList *vargs = procdecl->data.proc_decl.var_args;
+    while (vargs) {
+      printf("%s", vargs->node->data.variable.name);
+      vargs = vargs->next;
+      if (vargs) printf(", ");
+    }
+    printf(")\n");
+  }
+  imp_interpreter_context_proc_iter_destroy(iter);
 }
\ No newline at end of file
diff --git a/src/hashmap.c b/src/hashmap.c
deleted file mode 100644
index 89d0106..0000000
--- a/src/hashmap.c
+++ /dev/null
@@ -1,160 +0,0 @@
-#include "hashmap.h"
-
-#include <stdlib.h>
-#include <string.h>
-#include <assert.h>
-
-
-#define INITIAL_SIZE (16)
-#define LOAD_FACTOR_THRESHOLD (0.75)
-
-
-typedef struct Pair {
-  char *key;
-  void *element;
-  struct Pair *next;
-} Pair;
-
-typedef struct HashMap {
-  Pair **table;
-  size_t size;
-  size_t count;
-} HashMap;
-
-typedef struct HashMapKeysIter {
-  HashMap *map;
-  size_t bucket_index;
-  Pair *current;
-} HashMapKeysIter;
-
-
-static unsigned int hash(const char *key, size_t size) {
-  unsigned int hash_value = 0;
-  while (*key) hash_value = (hash_value * 31) + *key++;
-  return hash_value % size;
-}
-
-static void resize(HashMap *map) {
-  size_t new_size = map->size * 2;
-  Pair **new_table = (Pair**)calloc(new_size, sizeof(Pair*));
-  assert(new_table);
-  for (size_t i = 0; i < map->size; ++i) {
-    Pair *pair = map->table[i];
-    while (pair) {
-      unsigned int index = hash(pair->key, new_size);
-      Pair *next = pair->next;
-      pair->next = new_table[index];
-      new_table[index] = pair;
-      pair = next;
-    }
-  }
-  
-  free(map->table);
-  map->table = new_table;
-  map->size = new_size;
-}
-
-HashMap *hashmap_create(void) {
-  HashMap *map = (HashMap*)malloc(sizeof(HashMap));
-  assert(map);
-  map->size = INITIAL_SIZE;
-  map->count = 0;
-  map->table = (Pair**)calloc(map->size, sizeof(Pair*));
-  assert(map->table);
-  return map;
-}
-
-void hashmap_insert(HashMap *map, const char *key, void *element) {
-  void **old_value = hashmap_get(map, key);
-  if (old_value) {
-    *old_value = element;
-    return;
-  }
-  if ((float)map->count / map->size > LOAD_FACTOR_THRESHOLD) resize(map);
-  unsigned int index = hash(key, map->size);
-  Pair *new_pair = (Pair*)malloc(sizeof(Pair));
-  assert(new_pair);
-  new_pair->key = strdup(key);
-  assert(new_pair->key);
-  new_pair->element = element;
-  new_pair->next = map->table[index];
-  map->table[index] = new_pair;
-  map->count++;
-}
-
-void **hashmap_get(HashMap *map, const char *key) {
-  unsigned int index = hash(key, map->size);
-  Pair *pair = map->table[index];
-  while (pair) {
-    if (strcmp(pair->key, key) == 0) return &pair->element;
-    pair = pair->next;
-  }
-  return NULL;
-}
-
-int hashmap_delete(HashMap *map, const char *key) {
-  unsigned int index = hash(key, map->size);
-  Pair *pair = map->table[index];
-  Pair *prev = NULL;
-  while (pair) {
-    if (strcmp(pair->key, key) == 0) {
-      if (prev) prev->next = pair->next;
-      else map->table[index] = pair->next;
-      free(pair->key);
-      free(pair);
-      map->count--;
-      return 0;
-    }
-    prev = pair;
-    pair = pair->next;
-  }
-  return -1;
-}
-
-void hashmap_free(HashMap *map) {
-  for (size_t i = 0; i < map->size; ++i) {
-    Pair *pair = map->table[i];
-    while (pair) {
-      Pair *temp = pair;
-      pair = pair->next;
-      free(temp->key);
-      free(temp);
-    }
-  }
-  free(map->table);
-  free(map);
-}
-
-HashMapKeysIter *hashmap_keys_iter_create(HashMap *map) {
-  HashMapKeysIter *iter = (HashMapKeysIter*)malloc(sizeof(HashMapKeysIter));
-  assert(iter);
-  iter->map = map;
-  iter->bucket_index = 0;
-  iter->current = NULL;
-  while (iter->bucket_index < map->size && map->table[iter->bucket_index] == NULL) {
-    iter->bucket_index++;
-  }
-  if (iter->bucket_index < map->size) {
-    iter->current = map->table[iter->bucket_index];
-  }
-  return iter;
-}
-
-const char *hashmap_keys_iter_next(HashMapKeysIter *iter) {
-  if (!iter->current) return NULL;
-  const char *key = iter->current->key;
-  if (iter->current->next) {
-    iter->current = iter->current->next;
-  } else {
-    iter->bucket_index++;
-    while (iter->bucket_index < iter->map->size && iter->map->table[iter->bucket_index] == NULL) {
-      iter->bucket_index++;
-    }
-    iter->current = (iter->bucket_index < iter->map->size) ? iter->map->table[iter->bucket_index] : NULL;
-  }
-  return key;
-}
-
-void hashmap_keys_iter_free(HashMapKeysIter *iter) {
-  free(iter);
-}
\ No newline at end of file
diff --git a/src/interpreter.c b/src/interpreter.c
index c0678b7..b04a293 100644
--- a/src/interpreter.c
+++ b/src/interpreter.c
@@ -4,248 +4,18 @@
 #include <stdio.h>
 #include <assert.h>
 
-#include "hashmap.h"
 
-
-typedef void *YY_BUFFER_STATE;
-extern FILE *yyin;
-extern IMP_ASTNode *ast_root;
-extern int yyparse(void);
-extern void yyrestart (FILE*);
-extern YY_BUFFER_STATE yy_scan_string(const char*);
-extern void yy_delete_buffer(YY_BUFFER_STATE);
-
-typedef struct Context{
-  hashmap_t var_table;
-  hashmap_t proc_table;
-} Context;
-
-
-static IMP_ASTNode *context_get_proc(Context *context, const char *name) {
-  IMP_ASTNode **procdecl = (IMP_ASTNode**)hashmap_get(context->proc_table, name);
-  if (procdecl) return *procdecl;
-  return NULL;
-}
-
-static void context_set_proc(Context *context, const char *name, IMP_ASTNode *procdecl) {
-  hashmap_insert(context->proc_table, name, (void*)procdecl);
-}
-
-Context *context_create(void) {
-  Context *context = malloc(sizeof(Context));
-  assert(context);
-  context->var_table = hashmap_create();
-  context->proc_table = hashmap_create();
-  return context;
-}
-
-void context_free(Context *context) {
-  hashmap_free(context->var_table);
-  hashmap_keys_iter_t iter = hashmap_keys_iter_create(context->proc_table);
-  const char *key;
-  while ((key = hashmap_keys_iter_next(iter)) != NULL) {
-    IMP_ASTNode *procdecl = context_get_proc(context, key);
-    assert(procdecl);
-    imp_ast_free(procdecl);
-  }
-  hashmap_keys_iter_free(iter);
-  hashmap_free(context->proc_table);
-  free(context);
-}
-
-int context_get_var(Context *context, const char *name) {
-  int *val = (int*)hashmap_get(context->var_table, name);
-  if (val) return *val;
-  return 0;
-}
-
-void context_set_var(Context *context, const char *name, int val) {
-  hashmap_insert(context->var_table, name, (void*)val);
-}
-
-void context_print_var_table(Context *context) {
-  hashmap_keys_iter_t iter = hashmap_keys_iter_create(context->var_table);
-  const char *key;
-  while ((key = hashmap_keys_iter_next(iter)) != NULL) {
-    int val = context_get_var(context, key);
-    printf("%s = %d\n", key, val);
-  }
-  hashmap_keys_iter_free(iter);
-}
-
-void context_print_proc_table(Context *context) {
-  hashmap_keys_iter_t iter = hashmap_keys_iter_create(context->proc_table);
-  const char *key;
-  while ((key = hashmap_keys_iter_next(iter)) != NULL) {
-    IMP_ASTNode *procdecl = context_get_proc(context, key);
-    printf("%s(", key);
-    IMP_ASTNodeList *args = procdecl->data.proc_decl.val_args;
-    while (args) {
-      printf("%s", args->node->data.variable.name);
-      args = args->next;
-      if (args) printf(", ");
-    }
-    printf("; ");
-    IMP_ASTNodeList *vargs = procdecl->data.proc_decl.var_args;
-    while (vargs) {
-      printf("%s", vargs->node->data.variable.name);
-      vargs = vargs->next;
-      if (vargs) printf(", ");
-    }
-    printf(")\n");
-  }
-  hashmap_keys_iter_free(iter);
-}
-
-void ast_print(IMP_ASTNode *node, int depth) {
-  int indent = depth * 2;
-  switch (node->type) {
-    case IMP_AST_NT_SKIP: {
-      printf("%*sSKIP\n", indent, "");
-      break;
-    }
-    case IMP_AST_NT_ASSIGN: {
-      printf("%*sASSIGN %s=", indent, "", 
-             node->data.assign.var->data.variable.name);
-      ast_print(node->data.assign.aexpr, 0);
-      printf("\n");
-      break;
-    }
-    case IMP_AST_NT_SEQ: {
-      ast_print(node->data.seq.fst_stmt, depth);
-      printf("%*sSEQ\n", indent, "");
-      ast_print(node->data.seq.snd_stmt, depth);
-      break;
-    }
-    case IMP_AST_NT_IF: {
-      printf("%*sIF (", indent, "");
-      ast_print(node->data.if_stmt.cond_bexpr, 0);
-      printf(")\n");
-      ast_print(node->data.if_stmt.then_stmt, depth + 1);
-      printf("%*sELSE\n", indent, "");
-      ast_print(node->data.if_stmt.else_stmt, depth + 1);
-      break;
-    }
-    case IMP_AST_NT_WHILE: {
-      printf("%*sWHILE (", indent, "");
-      ast_print(node->data.while_stmt.cond_bexpr, 0);
-      printf(")\n");
-      ast_print(node->data.while_stmt.body_stmt, depth + 1);
-      break;
-    }
-    case IMP_AST_NT_INT: {
-      printf("%d", node->data.integer.val);
-      break;
-    }
-    case IMP_AST_NT_VAR: {
-      printf("%s", node->data.variable.name);
-      break;
-    }
-    case IMP_AST_NT_AOP: {
-      printf("(");
-      ast_print(node->data.arith_op.l_aexpr, 0);
-      switch (node->data.arith_op.aopr) {
-        case IMP_AST_AOP_ADD: printf(" + "); break;
-        case IMP_AST_AOP_SUB: printf(" - "); break;
-        case IMP_AST_AOP_MUL: printf(" * "); break;
-        default: assert(0);
-      }
-      ast_print(node->data.arith_op.r_aexpr, 0);
-      printf(")");
-      break;
-    }
-    case IMP_AST_NT_BOP: {
-      printf("(");
-      ast_print(node->data.bool_op.l_bexpr, 0);
-      switch (node->data.bool_op.bopr) {
-        case IMP_AST_BOP_AND: printf(" && "); break;
-        case IMP_AST_BOP_OR:  printf(" || "); break;
-        default: assert(0);
-      }
-      ast_print(node->data.bool_op.r_bexpr, 0);
-      printf(")");
-      break;
-    }
-    case IMP_AST_NT_NOT: {
-      printf("!");
-      ast_print(node->data.bool_not.bexpr, 0);
-      break;
-    }
-    case IMP_AST_NT_ROP: {
-      printf("(");
-      ast_print(node->data.rel_op.l_aexpr, 0);
-      switch (node->data.rel_op.ropr) {
-        case IMP_AST_ROP_EQ: printf(" == "); break;
-        case IMP_AST_ROP_NE: printf(" != "); break;
-        case IMP_AST_ROP_LT: printf(" < "); break;
-        case IMP_AST_ROP_LE: printf(" <= "); break;
-        case IMP_AST_ROP_GT: printf(" > "); break;
-        case IMP_AST_ROP_GE: printf(" >= "); break;
-        default: assert(0);
-      }
-      ast_print(node->data.rel_op.r_aexpr, 0);
-      printf(")");
-      break;
-    }
-    case IMP_AST_NT_LET: {
-      printf("%*sLET %s = ", indent, "", node->data.let_stmt.var->data.variable.name);
-      ast_print(node->data.let_stmt.aexpr, 0);
-      printf("\n");
-      ast_print(node->data.let_stmt.body_stmt, depth + 1);
-      break;
-    }
-    case IMP_AST_NT_PROCDECL: {
-      printf("%*sPROC %s(", indent, "", node->data.proc_decl.name);
-      IMP_ASTNodeList *args = node->data.proc_decl.val_args;
-      while (args) {
-        printf("%s", args->node->data.variable.name);
-        args = args->next;
-        if (args) printf(", ");
-      }
-      printf("; ");
-      IMP_ASTNodeList *vargs = node->data.proc_decl.var_args;
-      while (vargs) {
-        printf("%s", vargs->node->data.variable.name);
-        vargs = vargs->next;
-        if (vargs) printf(", ");
-      }
-      printf(")\n");
-      ast_print(node->data.proc_decl.body_stmt, depth + 1);
-      break;
-    }
-    case IMP_AST_NT_PROCCALL: {
-      printf("%*sCALL %s(", indent, "", node->data.proc_call.name);
-      IMP_ASTNodeList *args = node->data.proc_call.val_args;
-      while (args) {
-        printf("%s", args->node->data.variable.name);
-        args = args->next;
-        if (args) printf(", ");
-      }
-      printf("; ");
-      IMP_ASTNodeList *vargs = node->data.proc_call.var_args;
-      while (vargs) {
-        printf("%s", vargs->node->data.variable.name);
-        vargs = vargs->next;
-        if (vargs) printf(", ");
-      }
-      printf(")\n");
-      break;
-    }
-    default: assert(0);
-  }
-}
-
-static int eval_aexpr(Context *context, IMP_ASTNode *node) {
+static int eval_aexpr(IMP_InterpreterContext *context, const IMP_ASTNode *node) {
   switch (node->type) {
     case IMP_AST_NT_INT: return node->data.integer.val;
-    case IMP_AST_NT_VAR: return context_get_var(context, node->data.variable.name);
+    case IMP_AST_NT_VAR: return imp_interpreter_context_var_get(context, node->data.variable.name);
     case IMP_AST_NT_AOP: {
-      int aexp1_val = eval_aexpr(context, node->data.arith_op.l_aexpr);
-      int aexp2_val = eval_aexpr(context, node->data.arith_op.r_aexpr);
+      int l_val = eval_aexpr(context, node->data.arith_op.l_aexpr);
+      int r_val = eval_aexpr(context, node->data.arith_op.r_aexpr);
       switch (node->data.arith_op.aopr) {
-        case IMP_AST_AOP_ADD: return aexp1_val + aexp2_val;
-        case IMP_AST_AOP_SUB: return aexp1_val - aexp2_val;
-        case IMP_AST_AOP_MUL: return aexp1_val * aexp2_val;
+        case IMP_AST_AOP_ADD: return l_val + r_val;
+        case IMP_AST_AOP_SUB: return l_val - r_val;
+        case IMP_AST_AOP_MUL: return l_val * r_val;
         default: assert(0);
       }
     }
@@ -253,28 +23,28 @@ static int eval_aexpr(Context *context, IMP_ASTNode *node) {
   }
 }
 
-static int eval_bexpr(Context *context, IMP_ASTNode *node) {
+static int eval_bexpr(IMP_InterpreterContext *context, const IMP_ASTNode *node) {
   switch (node->type) {
     case IMP_AST_NT_BOP: {
-      int bexp1_val = eval_bexpr(context, node->data.bool_op.l_bexpr);
-      int bexp2_val = eval_bexpr(context, node->data.bool_op.r_bexpr);
+      int l_val = eval_bexpr(context, node->data.bool_op.l_bexpr);
+      int r_val = eval_bexpr(context, node->data.bool_op.r_bexpr);
       switch (node->data.bool_op.bopr) {
-        case IMP_AST_BOP_AND: return bexp1_val && bexp2_val;
-        case IMP_AST_BOP_OR:  return bexp1_val || bexp2_val;
+        case IMP_AST_BOP_AND: return l_val && r_val;
+        case IMP_AST_BOP_OR:  return l_val || r_val;
         default: assert(0);
       }
     }
     case IMP_AST_NT_NOT: return !eval_bexpr(context, node->data.bool_not.bexpr);
     case IMP_AST_NT_ROP: {
-      int aexp1_val = eval_aexpr(context, node->data.rel_op.l_aexpr);
-      int aexp2_val = eval_aexpr(context, node->data.rel_op.r_aexpr);
+      int l_val = eval_aexpr(context, node->data.rel_op.l_aexpr);
+      int r_val = eval_aexpr(context, node->data.rel_op.r_aexpr);
       switch (node->data.rel_op.ropr) {
-        case IMP_AST_ROP_EQ: return aexp1_val == aexp2_val;
-        case IMP_AST_ROP_NE: return aexp1_val != aexp2_val;
-        case IMP_AST_ROP_LT: return aexp1_val < aexp2_val;
-        case IMP_AST_ROP_LE: return aexp1_val <= aexp2_val;
-        case IMP_AST_ROP_GT: return aexp1_val > aexp2_val;
-        case IMP_AST_ROP_GE: return aexp1_val >= aexp2_val;
+        case IMP_AST_ROP_EQ: return l_val == r_val;
+        case IMP_AST_ROP_NE: return l_val != r_val;
+        case IMP_AST_ROP_LT: return l_val < r_val;
+        case IMP_AST_ROP_LE: return l_val <= r_val;
+        case IMP_AST_ROP_GT: return l_val > r_val;
+        case IMP_AST_ROP_GE: return l_val >= r_val;
         default: assert(0);
       }
     }
@@ -282,155 +52,98 @@ static int eval_bexpr(Context *context, IMP_ASTNode *node) {
   }
 }
 
-static int interp_proccall(Context *context, IMP_ASTNode *node) {
+static int interpret_proccall(IMP_InterpreterContext *context, const IMP_ASTNode *node) {
   const char *name = node->data.proc_call.name;
-  IMP_ASTNode *procdecl = context_get_proc(context, name);
+  const IMP_ASTNode *procdecl = imp_interpreter_context_proc_get(context, name);
   if (!procdecl) {
     fprintf(stderr, "Error: procedure %s not defined\n", name);
     return -1;
   }
-  IMP_ASTNodeList *caller_args = node->data.proc_call.val_args;
-  IMP_ASTNodeList *callee_args = procdecl->data.proc_decl.val_args;
-  Context *proc_context = context_create();
-  hashmap_keys_iter_t iter = hashmap_keys_iter_create(context->proc_table);
-  const char *key;
-  while ((key = hashmap_keys_iter_next(iter)) != NULL) {
-    IMP_ASTNode *proc = context_get_proc(context, key);
-    context_set_proc(proc_context, key, imp_ast_clone(proc));
-  }
-  hashmap_keys_iter_free(iter);
-  while (caller_args && callee_args) {
-    const char *caller_arg_name = caller_args->node->data.variable.name;
-    const char *callee_arg_name = callee_args->node->data.variable.name;
-    context_set_var(proc_context, callee_arg_name, context_get_var(context, caller_arg_name));
-    caller_args = caller_args->next;
-    callee_args = callee_args->next;
-  }
-  if (caller_args || callee_args) {
+  IMP_InterpreterContext *proc_context = imp_interpreter_context_create();
+  IMP_InterpreterContextProcIter *proc_iter = imp_interpreter_context_proc_iter_create(context);
+  const IMP_InterpreterContextProcTableEntry *proc_entry;
+  while ((proc_entry = imp_interpreter_context_proc_iter_next(proc_iter))) {
+    imp_interpreter_context_proc_set(proc_context, proc_entry->key, proc_entry->value);
+  }
+  imp_interpreter_context_proc_iter_destroy(proc_iter);
+  IMP_ASTNodeList *caller_val_args = node->data.proc_call.val_args;
+  IMP_ASTNodeList *callee_val_args = procdecl->data.proc_decl.val_args;
+  while (caller_val_args && callee_val_args) {
+    const char *caller_arg_name = caller_val_args->node->data.variable.name;
+    const char *callee_arg_name = callee_val_args->node->data.variable.name;
+    imp_interpreter_context_var_set(proc_context, callee_arg_name, imp_interpreter_context_var_get(context, caller_arg_name));
+    caller_val_args = caller_val_args->next;
+    callee_val_args = callee_val_args->next;
+  }
+  if (caller_val_args || callee_val_args) {
     fprintf(stderr, "Error: procedure %s called with wrong number of value arguments\n", name);
-    context_free(proc_context);
+    imp_interpreter_context_destroy(proc_context);
     return -1;
   }
-  if (interp_ast(proc_context, procdecl->data.proc_decl.body_stmt)) {
-    context_free(proc_context);
+  if (imp_interpreter_interpret_ast(proc_context, procdecl->data.proc_decl.body_stmt)) {
+    imp_interpreter_context_destroy(proc_context);
     return -1;
   }
-  IMP_ASTNodeList *caller_vargs = node->data.proc_call.var_args;
-  IMP_ASTNodeList *callee_vargs = procdecl->data.proc_decl.var_args;
-  while (caller_vargs && callee_vargs) {
-    const char *caller_varg_name = caller_vargs->node->data.variable.name;
-    const char *callee_varg_name = callee_vargs->node->data.variable.name;
-    context_set_var(context, caller_varg_name, context_get_var(proc_context, callee_varg_name));
-    caller_vargs = caller_vargs->next;
-    callee_vargs = callee_vargs->next;
+  IMP_ASTNodeList *caller_var_args = node->data.proc_call.var_args;
+  IMP_ASTNodeList *callee_var_args = procdecl->data.proc_decl.var_args;
+  while (caller_var_args && callee_var_args) {
+    const char *caller_varg_name = caller_var_args->node->data.variable.name;
+    const char *callee_varg_name = callee_var_args->node->data.variable.name;
+    imp_interpreter_context_var_set(context, caller_varg_name, imp_interpreter_context_var_get(proc_context, callee_varg_name));
+    caller_var_args = caller_var_args->next;
+    callee_var_args = callee_var_args->next;
   }
-  if (caller_vargs || callee_vargs) {
+  if (caller_var_args || callee_var_args) {
     fprintf(stderr, "Error: procedure %s called with wrong number of variable arguments\n", name);
-    context_free(proc_context);
+    imp_interpreter_context_destroy(proc_context);
     return -1;
   }
-  context_free(proc_context);
+  imp_interpreter_context_destroy(proc_context);
   return 0;
 }
 
-int interp_ast(Context *context, IMP_ASTNode *node) {
+int imp_interpreter_interpret_ast(IMP_InterpreterContext *context, const IMP_ASTNode *node) {
   switch (node->type) {
     case IMP_AST_NT_SKIP: return 0;
     case IMP_AST_NT_ASSIGN: {
       const char *name = node->data.assign.var->data.variable.name;
       int val = eval_aexpr(context, node->data.assign.aexpr);
-      context_set_var(context, name, val);
+      imp_interpreter_context_var_set(context, name, val);
       return 0;
     }
     case IMP_AST_NT_SEQ:
-      if (interp_ast(context, node->data.seq.fst_stmt)) return -1;
-      if (interp_ast(context, node->data.seq.snd_stmt)) return -1;
+      if (imp_interpreter_interpret_ast(context, node->data.seq.fst_stmt)) return -1;
+      if (imp_interpreter_interpret_ast(context, node->data.seq.snd_stmt)) return -1;
       return 0;
     case IMP_AST_NT_IF:
-      if (eval_bexpr(context, node->data.if_stmt.cond_bexpr)) return interp_ast(context, node->data.if_stmt.then_stmt);
-      else return interp_ast(context, node->data.if_stmt.else_stmt);
+      if (eval_bexpr(context, node->data.if_stmt.cond_bexpr)) return imp_interpreter_interpret_ast(context, node->data.if_stmt.then_stmt);
+      else return imp_interpreter_interpret_ast(context, node->data.if_stmt.else_stmt);
     case IMP_AST_NT_WHILE:
       while (eval_bexpr(context, node->data.while_stmt.cond_bexpr)) {
-        if (interp_ast(context, node->data.while_stmt.body_stmt)) return -1;
+        if (imp_interpreter_interpret_ast(context, node->data.while_stmt.body_stmt)) return -1;
       }
       return 0;
     case IMP_AST_NT_LET: {
       const char *name = node->data.let_stmt.var->data.variable.name;
-      int old_val = context_get_var(context, name);
+      int old_val = imp_interpreter_context_var_get(context, name);
       int new_val = eval_aexpr(context, node->data.let_stmt.aexpr);
-      context_set_var(context, name, new_val);
-      int ret = interp_ast(context, node->data.let_stmt.body_stmt);
-      context_set_var(context, name, old_val);
+      imp_interpreter_context_var_set(context, name, new_val);
+      int ret = imp_interpreter_interpret_ast(context, node->data.let_stmt.body_stmt);
+      imp_interpreter_context_var_set(context, name, old_val);
       return ret;
     }
     case IMP_AST_NT_PROCDECL: {
       const char *name = node->data.proc_decl.name;
-      IMP_ASTNode *procdecl_old = context_get_proc(context, name);
-      if (procdecl_old) {
+      if (imp_interpreter_context_proc_get(context, name)) {
         fprintf(stderr, "Error: procedure %s already defined\n", name);
         return -1;
       }
-      IMP_ASTNode *procdecl = imp_ast_clone(node);
-      context_set_proc(context, name, procdecl);
+      imp_interpreter_context_proc_set(context, name, node);
       return 0;
     }
     case IMP_AST_NT_PROCCALL: {
-      return interp_proccall(context, node);
+      return interpret_proccall(context, node);
     }
     default: assert(0);
   }
-}
-
-int interp_file (Context *context, const char *path) {
-  yyin = fopen(path, "r");
-  if (!yyin) {
-    return -1;
-  }
-  yyrestart(yyin);
-  if (yyparse()) {
-    imp_ast_free(ast_root);
-    fclose(yyin);
-    return -1;
-  }
-  if (interp_ast(context, ast_root)) {
-    imp_ast_free(ast_root);
-    fclose(yyin);
-    return -1;
-  }
-  imp_ast_free(ast_root);
-  fclose(yyin);
-  return 0;
-}
-
-int interp_str (Context *context, const char *str) {
-  YY_BUFFER_STATE buf = yy_scan_string(str);
-  if (yyparse()) {
-    imp_ast_free(ast_root);
-    yy_delete_buffer(buf);
-    return -1;
-  }
-  if (interp_ast(context, ast_root)) {
-    imp_ast_free(ast_root);
-    yy_delete_buffer(buf);
-    return -1;
-  }
-  yy_delete_buffer(buf);
-  return 0;
-}
-
-int print_ast_file (const char *path) {
-  yyin = fopen(path, "r");
-  if (!yyin) {
-    return -1;
-  }
-  yyrestart(yyin);
-  if (yyparse()) {
-    imp_ast_free(ast_root);
-    fclose(yyin);
-    return -1;
-  }
-  ast_print(ast_root, 0);
-  imp_ast_free(ast_root);
-  fclose(yyin);
-  return 0;
 }
\ No newline at end of file
diff --git a/src/interpreter_context.c b/src/interpreter_context.c
new file mode 100644
index 0000000..488f872
--- /dev/null
+++ b/src/interpreter_context.c
@@ -0,0 +1,123 @@
+#include "interpreter_context.h"
+
+#define STB_DS_IMPLEMENTATION
+#include "3rdparty/stb_ds/stb_ds.h"
+
+
+struct IMP_InterpreterContext {
+  IMP_InterpreterContextVarTableEntry *var_table;
+  IMP_InterpreterContextProcTableEntry *proc_table;
+};
+
+struct IMP_InterpreterContextVarIter {
+  IMP_InterpreterContextVarTableEntry *var_table;
+  ptrdiff_t index;
+  ptrdiff_t len;
+};
+
+struct IMP_InterpreterContextProcIter {
+  IMP_InterpreterContextProcTableEntry *proc_table;
+  ptrdiff_t index;
+  ptrdiff_t len;
+};
+
+IMP_InterpreterContext *imp_interpreter_context_create(void) {
+  IMP_InterpreterContext *context = malloc(sizeof(IMP_InterpreterContext));
+  assert(context && "Memory allocation failed");
+  context->var_table = NULL;
+  context->proc_table = NULL;
+  return context;
+}
+
+void imp_interpreter_context_destroy(IMP_InterpreterContext *context) {
+  ptrdiff_t len = shlen(context->var_table);
+  for (ptrdiff_t i = 0; i < len; ++i) free((char*)context->var_table[i].key);
+  shfree(context->var_table);
+}
+
+int imp_interpreter_context_var_get(IMP_InterpreterContext *context, const char *name) {
+  ptrdiff_t index = shgeti(context->var_table, name);
+  if (index < 0) return 0;
+  return context->var_table[index].value;
+}
+
+void imp_interpreter_context_var_set(IMP_InterpreterContext *context, const char *name, int value) {
+  ptrdiff_t index = shgeti(context->var_table, name);
+  if (index < 0) {
+    if (value == 0) return;
+    const char* key = strdup(name);
+    assert(key && "Memory allocation failed");
+    shput(context->var_table, key, value);
+  } else {
+    if (value == 0) {
+      const char *key = context->var_table[index].key;
+      shdel(context->var_table, name);
+      free((char*)key);
+      return;
+    }
+    context->var_table[index].value = value;
+  }
+}
+
+const IMP_ASTNode *imp_interpreter_context_proc_get(IMP_InterpreterContext *context, const char *name) {
+  ptrdiff_t index = shgeti(context->proc_table, name);
+  if (index < 0) return NULL;
+  return context->proc_table[index].value;
+}
+
+void imp_interpreter_context_proc_set(IMP_InterpreterContext *context, const char *name, const IMP_ASTNode *proc) {
+  ptrdiff_t index = shgeti(context->proc_table, name);
+  proc = imp_ast_clone(proc);
+  if (proc) assert(proc->type == IMP_AST_NT_PROCDECL);
+  if (index < 0) {
+    if (proc == NULL) return;
+    const char* key = strdup(name);
+    assert(key && "Memory allocation failed");
+    shput(context->proc_table, key, proc);
+  } else {
+    imp_ast_destroy((IMP_ASTNode*)context->proc_table[index].value);
+    if (proc == NULL) {
+      const char *key = context->proc_table[index].key;
+      shdel(context->proc_table, name);
+      free((char*)key);
+      return;
+    }
+    context->proc_table[index].value = proc;
+  }
+}
+
+IMP_InterpreterContextVarIter *imp_interpreter_context_var_iter_create(IMP_InterpreterContext *context) {
+  IMP_InterpreterContextVarIter *iter = malloc(sizeof(IMP_InterpreterContextVarIter));
+  assert(iter && "Memory allocation failed");
+  iter->var_table = context->var_table;
+  iter->index = 0;
+  iter->len = shlen(context->var_table);
+  return iter;
+}
+
+void imp_interpreter_context_var_iter_destroy(IMP_InterpreterContextVarIter *iter) {
+  free(iter);
+}
+
+IMP_InterpreterContextVarTableEntry *imp_interpreter_context_var_iter_next(IMP_InterpreterContextVarIter *iter) {
+  if (iter->index >= iter->len) return NULL;
+  return &iter->var_table[iter->index++];
+}
+
+IMP_InterpreterContextProcIter *imp_interpreter_context_proc_iter_create(IMP_InterpreterContext *context) {
+  IMP_InterpreterContextProcIter *iter = malloc(sizeof(IMP_InterpreterContextProcIter));
+  assert(iter && "Memory allocation failed");
+  iter->proc_table = context->proc_table;
+  iter->index = 0;
+  iter->len = shlen(context->proc_table);
+  return iter;
+}
+
+void imp_interpreter_context_proc_iter_destroy(IMP_InterpreterContextProcIter *iter) {
+  free(iter);
+}
+
+IMP_InterpreterContextProcTableEntry *imp_interpreter_context_proc_iter_next(IMP_InterpreterContextProcIter *iter) {
+  if (iter->index >= iter->len) return NULL;
+  return &iter->proc_table[iter->index++];
+}
\ No newline at end of file
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..5ef854d
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "interpreter_context.h"
+#include "driver.h"
+#include "repl.h"
+
+
+static int interpret_file(const char *path) {
+  IMP_InterpreterContext *context = imp_interpreter_context_create();
+  if (imp_driver_interpret_file(context, path)) {
+    fprintf(stderr, "Error interpreting file: %s\n", path);
+    imp_interpreter_context_destroy(context);
+    return -1;
+  }
+  imp_driver_print_var_table(context);
+  imp_interpreter_context_destroy(context);
+  return 0;
+}
+
+int main(int argc, char **argv) {
+  int opt;
+  while ((opt = getopt(argc, argv, "i:a:h")) != -1) {
+    switch (opt) {
+    case 'i': 
+      return interpret_file(optarg) ? EXIT_FAILURE : EXIT_SUCCESS;
+    case 'a':
+      return imp_driver_print_ast_file(optarg) ? EXIT_FAILURE : EXIT_SUCCESS;
+    case 'h':
+    default:
+      fprintf(stderr, 
+        "Usage: %s [ARGS]\n"
+        "  (no args)          start REPL\n"
+        "  -i <program.imp>   interpret program\n"
+        "  -a <program.imp>   print ast\n"
+        "  -h                 print this message\n",
+        argv[0]);
+      return (opt == 'h') ? EXIT_SUCCESS : EXIT_FAILURE;
+    }
+  }
+  imp_repl();
+  return EXIT_SUCCESS;
+}
\ No newline at end of file
diff --git a/src/repl.c b/src/repl.c
index 199c110..b553aec 100644
--- a/src/repl.c
+++ b/src/repl.c
@@ -8,7 +8,8 @@
 #include <readline/readline.h>
 #include <readline/history.h>
 
-#include "interpreter.h"
+#include "interpreter_context.h"
+#include "driver.h"
 
 
 static void print_help(void) {
@@ -31,7 +32,7 @@ static int is_valid_identifier(const char *var) {
   return 1;
 }
 
-static void repl_exec_command(context_t context, char *command) {
+static void repl_exec_command(IMP_InterpreterContext *context, char *command) {
   char *cmd = strtok(command, " \t");
   if (strcmp(cmd, "%quit") == 0) {
     exit(EXIT_SUCCESS);
@@ -40,7 +41,8 @@ static void repl_exec_command(context_t context, char *command) {
   } else if (strcmp(cmd, "%run") == 0) {
     char *file = strtok(NULL, " \t");
     if (file) {
-      if (!interp_file(context, file)) context_print_var_table(context);
+      if (!imp_driver_interpret_file(context, file)) imp_driver_print_var_table(context);
+      else fprintf(stderr, "Error interpreting file: %s\n", file);
     } else {
       fprintf(stderr, "Usage: %%run <path/to/file.imp>\n");
     }
@@ -49,7 +51,7 @@ static void repl_exec_command(context_t context, char *command) {
     char *val = strtok(NULL, " \t");
     if (var && val) {
       if (is_valid_identifier(var)) {
-        context_set_var(context, var, atoi(val));
+        imp_interpreter_context_var_set(context, var, atoi(val));
       } else {
         fprintf(stderr, "Invalid variable name: %s\n", var);
       }
@@ -58,28 +60,28 @@ static void repl_exec_command(context_t context, char *command) {
     char *var = strtok(NULL, " \t");
     if (var) {
       if (is_valid_identifier(var)) {
-        printf("%s = %d\n", var, context_get_var(context, var));
+        printf("%s = %d\n", var, imp_interpreter_context_var_get(context, var));
       } else {
         fprintf(stderr, "Invalid variable name: %s\n", var);
       }
-    } else context_print_var_table(context);
+    } else imp_driver_print_var_table(context);
   } else if (strcmp(cmd, "%procedures") == 0) {
-    context_print_proc_table(context);
+    imp_driver_print_proc_table(context);
   } else {
     fprintf(stderr, "Unknown command: %s\n", cmd);
   }
 }
 
-static void repl_exec_statement(context_t context, const char *statement) {
-  if (interp_str(context, statement)) {
+static void repl_exec_statement(IMP_InterpreterContext *context, const char *statement) {
+  if (imp_driver_interpret_str(context, statement)) {
     fprintf(stderr, "Error interpreting statement: %s\n", statement);
     return;
   }
-  context_print_var_table(context);
+  imp_driver_print_var_table(context);
 }
 
-void repl(void) {
-  context_t context = context_create();
+void imp_repl(void) {
+  IMP_InterpreterContext *context = imp_interpreter_context_create();
 
   char *line;
   print_help();
@@ -91,5 +93,5 @@ void repl(void) {
   }
   printf("\n");
 
-  context_free(context);
+  imp_interpreter_context_destroy(context);
 }
\ No newline at end of file
diff --git a/test/test.c b/test/test.c
new file mode 100644
index 0000000..a2f8a34
--- /dev/null
+++ b/test/test.c
@@ -0,0 +1,131 @@
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+#include "ast.h"
+#include "interpreter_context.h"
+#include "interpreter.h"
+
+static void test_interpreter_context(void) {
+  IMP_InterpreterContext *context = imp_interpreter_context_create();
+  assert(context);
+
+  int value;
+
+  value = imp_interpreter_context_var_get(context, "a");
+  assert(value == 0);
+
+  imp_interpreter_context_var_set(context, "a", 1);
+  value = imp_interpreter_context_var_get(context, "a");
+  assert(value == 1);
+
+  imp_interpreter_context_var_set(context, "b", 2);
+  value = imp_interpreter_context_var_get(context, "b");
+  assert(value == 2);
+
+  imp_interpreter_context_var_set(context, "c", 3);
+  value = imp_interpreter_context_var_get(context, "c");
+  assert(value == 3);
+
+  imp_interpreter_context_var_set(context, "a", 4);
+  value = imp_interpreter_context_var_get(context, "a");
+  assert(value == 4);
+
+  imp_interpreter_context_var_set(context, "b", 0);
+  value = imp_interpreter_context_var_get(context, "b");
+  assert(value == 0);
+
+  IMP_InterpreterContextVarIter *var_iter = imp_interpreter_context_var_iter_create(context);
+  IMP_InterpreterContextVarTableEntry *var_entry;
+  while ((var_entry = imp_interpreter_context_var_iter_next(var_iter))) {
+    if (strcmp(var_entry->key, "a") == 0) assert(var_entry->value == 4);
+    else if (strcmp(var_entry->key, "c") == 0) assert(var_entry->value == 3);
+    else assert(0);
+  }
+  imp_interpreter_context_var_iter_destroy(var_iter);
+
+  IMP_ASTNode *proc_a = imp_ast_procdecl("a", NULL, NULL, imp_ast_skip());
+  IMP_ASTNode *proc_b = imp_ast_procdecl("b", NULL, NULL, imp_ast_skip());
+  const IMP_ASTNode *proc;
+
+  proc = imp_interpreter_context_proc_get(context, "a");
+  assert(proc == NULL);
+
+  imp_interpreter_context_proc_set(context, "a", proc_a);
+  proc = imp_interpreter_context_proc_get(context, "a");
+  assert(proc != NULL);
+
+  imp_interpreter_context_proc_set(context, "b", proc_b);
+  proc = imp_interpreter_context_proc_get(context, "b");
+  assert(proc != NULL);
+
+  imp_interpreter_context_proc_set(context, "b", NULL);
+  proc = imp_interpreter_context_proc_get(context, "b");
+  assert(proc == NULL);
+
+  IMP_InterpreterContextProcIter *proc_iter = imp_interpreter_context_proc_iter_create(context);
+  IMP_InterpreterContextProcTableEntry *proc_entry;
+  while ((proc_entry = imp_interpreter_context_proc_iter_next(proc_iter))) {
+    if (strcmp(proc_entry->key, "a") == 0) assert(proc_entry->value != NULL);
+    else assert(0);
+  }
+  imp_interpreter_context_proc_iter_destroy(proc_iter);
+
+  imp_ast_destroy(proc_a);
+  imp_ast_destroy(proc_b);
+  
+  imp_interpreter_context_destroy(context);
+}
+
+static void test_interpreter(void) {
+  IMP_ASTNode *factorial_procdecl = imp_ast_procdecl(
+    "factorial",
+    imp_ast_list(imp_ast_var("n"), NULL),
+    imp_ast_list(imp_ast_var("r"), NULL),
+    imp_ast_if(
+      imp_ast_rop(IMP_AST_ROP_LE, imp_ast_var("n"), imp_ast_int(0)),
+      imp_ast_assign(imp_ast_var("r"), imp_ast_int(1)),
+      imp_ast_seq(
+        imp_ast_assign(imp_ast_var("m"), imp_ast_aop(IMP_AST_AOP_SUB, imp_ast_var("n"), imp_ast_int(1))),
+        imp_ast_seq(
+          imp_ast_proccall(
+            "factorial", 
+            imp_ast_list(imp_ast_var("m"), NULL),
+            imp_ast_list(imp_ast_var("r"), NULL)
+          ),
+          imp_ast_assign(imp_ast_var("r"), imp_ast_aop(IMP_AST_AOP_MUL, imp_ast_var("r"), imp_ast_var("n")))
+        )
+      )
+    )
+  );
+
+  IMP_ASTNode *main = imp_ast_seq(
+    factorial_procdecl,
+    imp_ast_seq(
+      imp_ast_assign(imp_ast_var("n"), imp_ast_int(5)),
+      imp_ast_proccall(
+        "factorial",
+        imp_ast_list(imp_ast_var("n"), NULL),
+        imp_ast_list(imp_ast_var("r"), NULL)
+      )
+    )
+  );
+
+  IMP_InterpreterContext *context = imp_interpreter_context_create();
+  int result = imp_interpreter_interpret_ast(context, main);
+  assert(result == 0);
+  int factorial_result = imp_interpreter_context_var_get(context, "r");
+  assert(factorial_result == 120);
+  const IMP_ASTNode *proc = imp_interpreter_context_proc_get(context, "factorial");
+  assert(proc != NULL);
+
+  imp_ast_destroy(main);
+  imp_interpreter_context_destroy(context);
+}
+
+int main(void) {
+  printf("Starting tests...\n");
+  test_interpreter_context();
+  test_interpreter();
+  printf("All tests passed\n");
+}
\ No newline at end of file