Added symbol support on parser

program.tf

@@ -1 +1 @@
-5 10 20
+5 10 20 + print

toyforth.c

@@ -63,8 +63,10 @@ tfobj *createObject(int type)
 tfobj *createStringObject(char *s, size_t len)
 {
     tfobj *obj = createObject(TFOBJ_TYPE_STR);
-    obj->str.ptr = s;
+    obj->str.ptr = xmalloc(len+1);
     obj->str.len = len;
+    memcpy(obj->str.ptr, s, len);
+    obj->str.ptr[len] = 0;
     return obj;
 }
 
@@ -137,6 +139,23 @@ tfobj *parseNumber(tfparser *parser)
     return obj;
 }
 
+/* Return true if the character 'c' is one of the characters
+ * acceptable for our symbols.
+ */
+int isSymbolChar(int c)
+{
+    char symchars[] = "+-*/%";
+    return isalpha(c) || strchr(symchars, c) != NULL;
+}
+
+tfobj *parseSymbol(tfparser *parser)
+{
+    char *start = parser->p;
+    while (parser->p[0] && isSymbolChar(parser->p[0])) parser->p++;
+    int len = parser->p - start;
+    return createSymbolObject(start, len);
+}
+
 tfobj *compile(char *prg)
 {
     tfparser parser;
@@ -152,8 +171,11 @@ tfobj *compile(char *prg)
         parseSpaces(&parser);
         if (parser.p[0] == 0) break; // End of program reached.
 
-        if (isdigit(parser.p[0]) || parser.p[0] == '-') {
+        if (isdigit(parser.p[0]) ||
+            (parser.p[0] == '-' && isdigit(parser.p[1]))) {
             obj = parseNumber(&parser);
+        } else if (isSymbolChar(parser.p[0])) {
+            obj = parseSymbol(&parser);
         } else {
             obj = NULL;
         }
@@ -173,21 +195,27 @@ tfobj *compile(char *prg)
 
 /* ############################ Execute the program ##################################### */
 
-void exec(tfobj *obj) {
+void printObject(tfobj *obj) {
-    // TODO: unimplmented function
+    switch (obj->type) {
+    case TFOBJ_TYPE_INT:
+        printf("%d", obj->i);
+        break;
+    case TFOBJ_TYPE_LIST:
+        printf("[");
         for (size_t j = 0; j < obj->list.len; j++) {
             tfobj *o = obj->list.ele[j];
-        switch (o->type) {
+            printObject(o);
-        case TFOBJ_TYPE_INT:
+            printf(" ");
-            printf("%d", o->i);
+        }
+        printf("]");
+        break;
+    case TFOBJ_TYPE_SYMBOL:
+        printf("'%s", obj->str.ptr);
         break;
     default:
         printf("?");
         break;
     }
-        printf(" ");
-    }
-    printf("\n");
 }
 
 /* ############################### Main ################################################# */
@@ -217,7 +245,7 @@ int main(int argc, char **argv)
     //printf("Program text: \"%s\"\n", prgtext);
 
     tfobj *prg = compile(prgtext);
-    exec(prg);
+    printObject(prg);
 
     return 0;
 }