pop_any(), pop_int(), and add

diff --git a/implementations/C/joy.c b/implementations/C/joy.c
index 1f8c91a..905eb7c 100644 (file)
--- a/implementations/C/joy.c
+++ b/implementations/C/joy.c
@@ -302,7 +302,51 @@ text_to_expression(char *text)
 }
 
 
-void add(JoyList *stack, JoyList *expression) {stack = expression;}
+JoyList
+pop_any(JoyList *stack) {
+       JoyList result;
+       if (!(*stack)) {
+               printf("Not enough values on stack.\n");
+               exit(1);
+       }
+       result = *stack;
+       *stack = (*stack)->tail;
+       return result;
+}
+
+mpz_t *
+pop_int(JoyList *stack) {
+       JoyList node;
+       node = pop_any(stack);
+       switch (node->head.kind) {
+       case joyInt:
+               return &(node->head.value.i);
+       default:
+               printf("Not an integer.\n");
+               exit(1);
+       }
+}
+
+void
+add(JoyList *stack, __attribute__((unused)) JoyList *expression)
+{
+       mpz_t *a, *b;
+       JoyList node;
+
+       a = pop_int(stack);
+       b = pop_int(stack);
+
+       node = newJoyList;
+       node->head.kind = joyInt;
+       mpz_init(node->head.value.i);
+       GC_register_finalizer(node->head.value.i, my_callback, NULL, NULL, NULL);
+       mpz_add(node->head.value.i, *a, *b);
+
+       node->tail = *stack;
+       *stack = node;
+}
+
+
 void branch(JoyList *stack, JoyList *expression) {stack = expression;}
 void clear(JoyList *stack, JoyList *expression) {stack = expression;}
 void div_joyfunc(JoyList *stack, JoyList *expression) {stack = expression;}