From d8a969e231135978c4dd1fa67559101f506ad6f3 Mon Sep 17 00:00:00 2001
From: Kai Stevenson <kai@kaistevenson.com>
Date: Wed, 5 Nov 2025 01:20:07 -0800
Subject: recursion works for types with depth limit 5

---
 src/lang/ts-lang/builtin/builtin.ts | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'src/lang/ts-lang/builtin/builtin.ts')

diff --git a/src/lang/ts-lang/builtin/builtin.ts b/src/lang/ts-lang/builtin/builtin.ts
index ed6b0a3..8532072 100644
--- a/src/lang/ts-lang/builtin/builtin.ts
+++ b/src/lang/ts-lang/builtin/builtin.ts
@@ -2,7 +2,9 @@ import { FnError } from ".";
 import {
   AddNumbers,
   AddStrings,
+  ArrayEqual,
   Multiply,
+  SubNumbers,
   ToString,
   UnarrayIfOnlyHead,
 } from "../util";
@@ -22,6 +24,16 @@ export type BUILTIN_Add<Args extends readonly any[]> =
     ? AddNumbers<Args>
     : FnError<`Cannot add operands ${ToString<Args>}`>;
 
+export type BUILTIN_Sub<Args extends readonly any[]> = Args extends [
+  infer A,
+  infer B,
+  infer C
+]
+  ? FnError<`Can only sub [number, number], but got ${ToString<Args>}`>
+  : Args extends [infer M extends number, infer N extends number]
+  ? SubNumbers<M, N>
+  : FnError<`Can only sub [number, number], but got ${ToString<Args>}`>;
+
 export type BUILTIN_Mul<Args extends readonly any[]> = Args extends [
   infer A,
   infer B,
@@ -32,6 +44,13 @@ export type BUILTIN_Mul<Args extends readonly any[]> = Args extends [
   ? Multiply<M, N>
   : FnError<`Can only multiply [number, number], but got ${ToString<Args>}`>;
 
+export type BUILTIN_Eq<Args extends readonly any[]> = Args extends
+  | readonly number[]
+  | readonly string[]
+  | readonly boolean[]
+  ? ArrayEqual<Args>
+  : FnError<`Can only check equality of numbers or string or boolean, but got ${ToString<Args>}`>;
+
 export type BUILTIN_IfElse<Args extends readonly any[]> = Args extends [
   infer A,
   infer B,
-- 
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