1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
|
#include "interpreter.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
static void env_update(Env **env, const char *name, int val) {
for (Env *e = *env; e; e = e->next) {
if (strcmp(e->name, name) == 0) {
e->val = val;
return;
}
}
Env *e = malloc(sizeof(Env));
e->name = strdup(name);
e->val = val;
e->next = *env;
*env = e;
}
static int env_lookup(Env **env, const char *name) {
for (Env *e = *env; e; e = e->next) {
if (strcmp(e->name, name) == 0)
return e->val;
}
env_update(env, name, 0);
return env_lookup(env, name);
}
void env_print(Env *env) {
Env *e = env;
while (e) {
printf("%s = %d\n", e->name, e->val);
e = e->next;
}
}
static int eval_aexpr(Env **env, ASTNode *node) {
switch (node->type) {
case NT_INT: return node->u.d_int.val;
case NT_VAR: return env_lookup(env, node->u.d_var.name);
case NT_AOP: {
int aexp1 = eval_aexpr(env, node->u.d_aop.aexp1);
int aexp2 = eval_aexpr(env, node->u.d_aop.aexp2);
switch (node->u.d_aop.aop) {
case AOP_ADD: return aexp1 + aexp2;
case AOP_SUB: return aexp1 - aexp2;
case AOP_MUL: return aexp1 * aexp2;
}
}
default:
fprintf(stderr, "Bad aexpr node %d\n", node->type);
exit(EXIT_FAILURE);
}
}
static int eval_bexpr(Env **env, ASTNode *node) {
switch (node->type) {
case NT_BOP: {
int bexp1 = eval_bexpr(env, node->u.d_bop.bexp1);
int bexp2 = eval_bexpr(env, node->u.d_bop.bexp2);
switch (node->u.d_bop.bop) {
case BOP_AND: return bexp1 && bexp2;
case BOP_OR: return bexp1 || bexp2;
}
}
case NT_NOT:
return !eval_bexpr(env, node->u.d_not.bexp);
case NT_ROP: {
int aexp1 = eval_aexpr(env, node->u.d_rop.aexp1);
int aexp2 = eval_aexpr(env, node->u.d_rop.aexp2);
switch (node->u.d_rop.rop) {
case ROP_EQ: return aexp1 == aexp2;
case ROP_NE: return aexp1 != aexp2;
case ROP_LT: return aexp1 < aexp2;
case ROP_LE: return aexp1 <= aexp2;
case ROP_GT: return aexp1 > aexp2;
case ROP_GE: return aexp1 >= aexp2;
}
}
default:
fprintf(stderr, "Bad bexpr node %d\n", node->type);
exit(EXIT_FAILURE);
}
}
void exec_stmt(Env **env, ASTNode *node) {
while (node) {
switch (node->type) {
case NT_SKIP:
return;
case NT_ASSIGN: {
char *var = node->u.d_assign.var->u.d_var.name;
int val = eval_aexpr(env, node->u.d_assign.aexp);
env_update(env, var, val);
return;
}
case NT_SEQ:
exec_stmt(env, node->u.d_seq.stm1);
exec_stmt(env, node->u.d_seq.stm2);
return;
case NT_IF:
if (eval_bexpr(env, node->u.d_if.bexp))
exec_stmt(env, node->u.d_if.stm1);
else
exec_stmt(env, node->u.d_if.stm2);
return;
case NT_WHILE:
while (eval_bexpr(env, node->u.d_while.bexp)) {
exec_stmt(env, node->u.d_while.stm);
}
return;
default:
fprintf(stderr, "Bad stmt node %d\n", node->type);
exit(EXIT_FAILURE);
}
}
}
|
