diff options
| -rw-r--r-- | README.md | 71 | ||||
| -rw-r--r-- | res/syntax.ebnf | 12 | ||||
| -rw-r--r-- | src/interpreter.c | 2 |
3 files changed, 76 insertions, 9 deletions
@@ -1,6 +1,19 @@ # IMP Interpreter -A small interpreter of the IMP programming language. +A small interpreter of the IMP programming language, written in *C* with *flex* for lexing and *bison* for parsing. +Currently the core functionality of IMP is implemented, additionally, the *local variable extension*, and the *procedure extension* also. Furthermore there are some syntactic enhancements, such as the boolean constants `true` and `false`, omitting parenthesis around expressions, and the ability to add arbitrary many semicolons after each statement. + + +## Dependencies + +- [flex](https://github.com/westes/flex) +- [bison](https://www.gnu.org/software/bison) +- [readline](https://tiswww.case.edu/php/chet/readline/rltop.html) + + +## Resources + +- [Formal Methods and Functional Programming (Course Webpage), ETHZ](https://infsec.ethz.ch/education/ss2025/fmfp.html) ## Build @@ -10,20 +23,34 @@ A small interpreter of the IMP programming language. - `make example` to interpret "example/example.imp". - `make clean` to remove build folder. +All build artifacts are created in the build folder `./build`, including the imp binary (`./build/imp`). -## Dependencies -- [flex](https://github.com/westes/flex) -- [bison](https://www.gnu.org/software/bison) -- [readline](https://tiswww.case.edu/php/chet/readline/rltop.html) +## Usage -## Resources +``` +Usage: imp [ARGS] + -i <program.imp> interpret program and exit + (no args) start REPL + -h show this message +``` -- [Formal Methods and Functional Programming (Course Webpage), ETHZ](https://infsec.ethz.ch/education/ss2025/fmfp.html) +### REPL +``` +IMP REPL (type IMP statements or commands starting with '%') +Commands: + %quit exit + %run <path/to/file.imp> interpret program + %set <var> <val> set variable + %print [<var>] print variable, or all variables + %help show this message +``` ## IMP +### Syntax + [Syntax](/res/syntax.ebnf) @@ -44,6 +71,11 @@ Control flow: - `(<stm>; <stm>)` sequential composition, the first statement runs before the second - `skip`, nop +Procedures: + +- `procedure <ident>(<var>, ... ; <var>, ... ) begin <stm> end` declaration, first argument list are value arguments (vars passed to procedure), second argument list are variable arguments (vars returned from procedure). +- `<ident>(<var>, ... ; <var>, ... )` call + **Expression** @@ -66,13 +98,36 @@ Boolean Expression `<bexp>`: - `<aexp> <= <aexp>` - `<aexp> > <aexp>` - `<aexp> >= <aexp>` +- `true` +- `false` **Variable `<var>`** -- `[a-zA-Z][A-Za-z0-9]*` +- `<ident>` **Numeral `<num>`** - `[0-9]+` + +**Identifier `<ident>`** + +- `[a-zA-Z][A-Za-z0-9]*` + +### Example + +``` +procedure factorial(n;r) begin + if n <= 0 then + r := 1; + else + m := n - 1; + factorial(m;r); + r := r * n; + end; +end; + +n := 5; +factorial(n;r); +```
\ No newline at end of file diff --git a/res/syntax.ebnf b/res/syntax.ebnf index 85990c5..af6b5ea 100644 --- a/res/syntax.ebnf +++ b/res/syntax.ebnf @@ -44,4 +44,16 @@ statement = "skip" | ( "if" , boolean_expression , "then" , statement , "else" , statement , "end" ) | ( "while" , boolean_expression , "do" , statement , "end" ) | ( "var" , variable , ":=", arithmetic_expression , "in" , statement , "end" ) + | proc_decl + | proc_call + ; + +arg_list = variable + | ( arg_list , "," , variable ) + ; + +proc_decl = "procedure" , identifier , "(" , arg_list , ";" , arg_list , ")" , "begin" , statement , "end" + ; + +proc_call = identifier , "(" , arg_list , ";" , arg_list , ")" ;
\ No newline at end of file diff --git a/src/interpreter.c b/src/interpreter.c index 9dc5a22..2f13ec0 100644 --- a/src/interpreter.c +++ b/src/interpreter.c @@ -208,7 +208,7 @@ int interp_ast(Context *context, ASTNode *node) { fprintf(stderr, "Error: procedure %s already defined\n", name); return -1; } - ASTNode *procdecl = ast_clone(node); + ASTNode *procdecl = ast_clone(node); context_set_proc(context, name, procdecl); return 0; } |