implemented drop builtin function

SLS_C/include/sls/interpreter.h

@@ -72,6 +72,7 @@ typedef struct {
 } FunctionItem;
 
 Boolean push_token(InterpreterState *interpreter_state, Token token);
+void clean_stack(StackItem *item);
 
 Boolean execute(InterpreterState *interpreter_state, LexerTokenResult *token);
 InterpreterState *interpreter_create();

SLS_C/src/builtin.c

@@ -789,8 +789,12 @@ Boolean builtin_depth(InterpreterState *interpreter_state) {
 }
 
 Boolean builtin_drop(InterpreterState *interpreter_state) {
-    (void)interpreter_state;
-    return FALSE;
+    StackItem *node = interpreter_state->stack;
+    if (node == NULL) return FALSE;
+    interpreter_state->stack = node->next;
+    node->next = NULL;
+    clean_stack(node);
+    return TRUE;
 }
 
 Boolean builtin_dup(InterpreterState *interpreter_state) {

SLS_C/src/interpreter.c

@@ -185,7 +185,7 @@ InterpreterState *interpreter_create() {
     return interpreter_state;
 }
 
-static void clean_stack(StackItem *item) {
+void clean_stack(StackItem *item) {
     if (item == NULL) return;
     if (item->type == STACK_TOKEN_STRING)
         clean_token_string(item->token_string);

SLS_C/src/repl.c

@@ -17,8 +17,10 @@
 static const SlsStr REPL_FILE_NAME = SLS_STR_CONST("<STDIN>");
 
 void print_top_of_stack(InterpreterState *interpreter_state) {
-    if (interpreter_state->stack == NULL)
+    if (interpreter_state->stack == NULL) {
+        printf("#0: <STACK IS EMPTY>\n");
         return;
+    }
     switch (interpreter_state->stack->type) {
     case STACK_IDENTIFIER:
         printf("#0: ::%s\n", interpreter_state->stack->identifier.name.str);