simple calculator example

1 files changed, 41 insertions, 19 deletions

diff --git a/lr-parser.c b/lr-parser.c
index 0d244fd..ad7dae5 100644
--- a/lr-parser.c
+++ b/lr-parser.c
@@ -20,23 +20,25 @@ typedef int stack_item;
 static stack_item stack_bottom[STACK_CAP];
 static stack_item *stack_head = stack_bottom;
 
-int lr_parser()
+int lr_parser(int *value)
 {
-#define push(item) ({ if(++stack_head - stack_bottom < STACK_CAP ) (*stack_head = item); else { fprintf(stderr, "ERROR: STACK_CAP exceeded\n"); return 1; }})
+#define push(item) do {                                                    \
+        if(++stack_head - stack_bottom < STACK_CAP ) *stack_head = item;   \
+        else { fprintf(stderr, "ERROR: STACK_CAP exceeded\n"); return 1; } \
+    } while(0)
 #define pop() (--stack_head)
 #define eat() toklist_eat()
-#define peek() ({                       \
-            symbol s = toklist_peek();  \
-            if(!symbol_is_valid(s)) { fprintf(stderr, "ERROR: Unknown token '%d'\n", s); return 1;} \
-            s; })
+#define peek() toklist_peek()
 
     while(1) {
-        struct action a = table[(size_t)*stack_head][peek()];
+        struct action a = table[(size_t)*stack_head][token_sym(peek())];
 
         switch(a.type) {
-        case ACTION_SHIFT:
-            push(eat());
-            push(-10000000); // the semantic action
+        case ACTION_SHIFT:;
+            struct token *t = eat();
+
+            push(token_sym(t));
+            push(token_val(t));
             push(a.arg);
             break;
         case ACTION_REDUCE:
@@ -57,12 +59,13 @@ int lr_parser()
             push(a_goto.arg);
             break;
         case ACTION_ACCEPT:
-            return *(stack_head-1);
+            *value =  *(stack_head-1);
+            return 0;
         case ACTION_NOT_SET:
         default:
             fprintf(stderr,
-                    "ERROR: Unexpected token '%d' at state %zu\n",
-                    peek(), (size_t)*stack_head);
+                    "ERROR: Unexpected symbol '%d' at state %zu\n",
+                    token_sym(peek()), (size_t)*stack_head);
             return 1;
         }
     }
@@ -124,19 +127,38 @@ struct action **table = (struct action *([])){
 
 size_t table_states = 13;
 
-// implement toklist
-static symbol toklist[] = {N0, PLUS, N1, END_INPUT};
-static symbol *tok = toklist;
+// implement toklist.h
+struct token {
+    symbol s;
+    int v;
+};
+
+static struct token toklist[] = {{N0}, {PLUS}, {N1}, {END_INPUT}};
+static const size_t ntoklist = sizeof(toklist)/sizeof(*toklist);
 
-symbol toklist_eat() { return *(tok++); } // unsafe
-symbol toklist_peek() { return *tok; }    // unsafe
+static size_t tok;
+
+struct token *toklist_eat()
+{
+    if(tok == ntoklist) return toklist + ntoklist-1;
+    return toklist + tok++;
+}
+struct token *toklist_peek() { return toklist + tok; }
+
+symbol token_sym(struct token *t) { return t->s; }
+int token_val(struct token *t)    { return t->v; }
 
 int none(int *stack_head) {(void)stack_head; return 0;}
 semantic_action_fn *semantic_actions = (semantic_action_fn[]){none, none, none, none, none, none, none, none};
 
 int main(void)
 {
-    return lr_parser();
+    int value;
+
+    if(lr_parser(&value)) return 1;
+    printf("%d\n", value);
+
+    return 0;
 }
 
 #endif