impl lots of arithmetic operations and if

lisp.c

@@ -25,14 +25,36 @@ static void scope_add_function(Scope *scope, const char *name,
     nob_da_append(scope, obj);
 }
 
+static bool node_is_true(Node node) {
+    switch (node.kind) {
+    case NODE_KIND_NUMBER:
+        return node.as_number != 0;
+    case NODE_KIND_LIST:
+        return node.as_list->count > 0;
+    default:
+        return true;
+    }
+}
+
 void build_scopes(Scopes *scopes) {
     // clang-format off
-    scope_add_function(&globalScope, "+", lisp_function_addition);
+    scope_add_function(&globalScope, "+", lisp_function_add);
+    scope_add_function(&globalScope, "-", lisp_function_sub);
+    scope_add_function(&globalScope, "/", lisp_function_div);
+    scope_add_function(&globalScope, "*", lisp_function_mul);
+    scope_add_function(&globalScope, "%", lisp_function_mod);
+    scope_add_function(&globalScope, "=", lisp_function_eq);
+    scope_add_function(&globalScope, "<", lisp_function_lt);
+    scope_add_function(&globalScope, ">", lisp_function_gt);
+    scope_add_function(&globalScope, "<=", lisp_function_lt_eq);
+    scope_add_function(&globalScope, ">=", lisp_function_gt_eq);
+
     scope_add_function(&globalScope, "println", lisp_function_println);
     scope_add_function(&globalScope, "list", lisp_function_list);
     scope_add_function(&globalScope, "append", lisp_function_append);
     scope_add_function(&globalScope, "length", lisp_function_length);
     scope_add_function(&globalScope, "null?", lisp_function_isnull);
+    scope_add_function(&globalScope, "builtins", lisp_function_builtins);
     // clang-format on
 
     nob_da_append(scopes, globalScope);
@@ -216,21 +238,34 @@ Node *eval(Node *node, Scopes *scopes) {
             return node;
 
         Node *head = &children->items[0];
-        Node *func_node = eval(head, scopes);
+        if (head->kind != NODE_KIND_SYMBOL)
+            return node;
 
         Nodes *args = malloc(sizeof(Nodes));
         for (size_t i = 1; i < children->count; i++) {
             nob_da_append(args, *eval(&children->items[i], scopes));
         }
 
-        if (func_node->kind == NODE_KIND_FUNCTION) {
-            return func_node->as_function.apply(args, scopes);
-        }
+        if (nob_sv_eq(head->as_symbol,
+                      (Nob_String_View){.count = 2, .data = "if"})) {
+            if (args->count != 3) {
+                printf("'if' expects three arguments!\n");
+                return NULL;
+            }
+            Node *condition = eval(&args->items[0], scopes);
+            return node_is_true(*condition) ? eval(&args->items[1], scopes)
+                                            : eval(&args->items[2], scopes);
+        } else {
+            Node *func_node = eval(head, scopes);
+            if (func_node->kind == NODE_KIND_FUNCTION) {
+                return func_node->as_function.apply(args, scopes);
+            }
 
-        printf("Not a function: '");
-        node_print(*func_node);
-        printf("'\n");
-        return NULL;
+            printf("Not a function: '");
+            node_print(*func_node);
+            printf("'\n");
+            return NULL;
+        }
     }
     default:
         UNREACHABLE("");