impl a bunch of builtins

builtins.c

@@ -1,7 +1,7 @@
 #include "lisp.h"
 
 Node *lisp_function_addition(Nodes *args, Scopes *scopes) {
-    (void)(scopes);
+    UNUSED(scopes);
 
     if (args->count != 2) {
         printf("'+' expects two arguments!\n");
@@ -35,3 +35,79 @@ Node *lisp_function_println(Nodes *args, Scopes *scopes) {
 
     return result;
 }
+
+Node *lisp_function_list(Nodes *args, Scopes *scopes) {
+    UNUSED(scopes);
+
+    Node *node = malloc(sizeof(Node));
+    node->kind = NODE_KIND_LIST;
+    node->as_list = args;
+    return node;
+}
+
+Node *lisp_function_append(Nodes *args, Scopes *scopes) {
+    UNUSED(scopes);
+
+    if (args->count != 2) {
+        printf("'append' expects two arguments!\n");
+        return NULL;
+    }
+
+    Node *node = malloc(sizeof(Node));
+    node->kind = NODE_KIND_LIST;
+
+    if (args->items[0].kind != NODE_KIND_LIST ||
+        args->items[1].kind != NODE_KIND_LIST) {
+        printf("'append' can only append two lists!\n");
+        return NULL;
+    }
+
+    Nodes *nodes = malloc(sizeof(Nodes));
+
+    Nodes *a = args->items[0].as_list;
+    nob_da_append_many(nodes, a->items, a->count);
+
+    Nodes *b = args->items[1].as_list;
+    nob_da_append_many(nodes, b->items, b->count);
+
+    node->as_list = nodes;
+    return node;
+}
+
+Node *lisp_function_length(Nodes *args, Scopes *scopes) {
+    UNUSED(scopes);
+
+    if (args->count != 1) {
+        printf("'length' expects one argument!\n");
+        return NULL;
+    }
+
+    if (args->items[0].kind != NODE_KIND_LIST) {
+        printf("'length' can only be used on lists!\n");
+        return NULL;
+    }
+
+    Node *node = malloc(sizeof(Node));
+    node->kind = NODE_KIND_NUMBER;
+    node->as_number = args->items[0].as_list->count;
+    return node;
+}
+
+Node *lisp_function_isnull(Nodes *args, Scopes *scopes) {
+    UNUSED(scopes);
+
+    if (args->count != 1) {
+        printf("'null?' expects one argument!\n");
+        return NULL;
+    }
+
+    if (args->items[0].kind != NODE_KIND_LIST) {
+        printf("'null?' can only be used on lists!\n");
+        return NULL;
+    }
+
+    Node *node = malloc(sizeof(Node));
+    node->kind = NODE_KIND_NUMBER;
+    node->as_number = args->items[0].as_list->count == 0 ? 1 : 0;
+    return node;
+}