From 632c153b974ee9c553d08beb27d5e4d60396a2ac Mon Sep 17 00:00:00 2001
From: Kai Stevenson <kai@kaistevenson.com>
Date: Sun, 2 Nov 2025 20:24:33 -0800
Subject: map index

---
 src/lang/builtin/sbuiltin.ts |  4 ++--
 src/lang/core/eval.ts        | 13 ++++++++-----
 src/lang/util/number.ts      |  3 +++
 3 files changed, 13 insertions(+), 7 deletions(-)

(limited to 'src')

diff --git a/src/lang/builtin/sbuiltin.ts b/src/lang/builtin/sbuiltin.ts
index f291de3..01f197e 100644
--- a/src/lang/builtin/sbuiltin.ts
+++ b/src/lang/builtin/sbuiltin.ts
@@ -1,6 +1,6 @@
 import { ASTNode, StackFrame } from "../core/common";
 import { CallFn, FnPrim, GetEvaluatedChildren, EvalError } from "../core/eval";
-import { ToString } from "../util";
+import { ExtractNumber, ToString } from "../util";
 
 export type SBUILTIN_Call<
   Node extends ASTNode,
@@ -21,7 +21,7 @@ export type SBUILTIN_Map<
   infer Arr extends readonly any[],
   infer Fn extends FnPrim
 ]
-  ? { [Idx in keyof Arr]: CallFn<Fn, [Arr[Idx]], Frame> }
+  ? { [Idx in keyof Arr]: CallFn<Fn, [Arr[Idx], ExtractNumber<Idx>], Frame> }
   : EvalError<`Invalid params for map: ${ToString<
       GetEvaluatedChildren<Node, Frame>
     >}`>;
diff --git a/src/lang/core/eval.ts b/src/lang/core/eval.ts
index 3dcf9b0..981aef8 100644
--- a/src/lang/core/eval.ts
+++ b/src/lang/core/eval.ts
@@ -52,15 +52,17 @@ export type FnPrim<
   Fn extends ASTNode = ASTNode
 > = { args: Args; fn: Fn };
 
-// Can support multiple args, just need to make the last arg be the fn
 export type HandleFn<Node extends ASTNode> = Node["children"] extends [
-  infer Arg extends ASTNode,
+  ...infer Args extends ASTNode[],
   infer Fn extends ASTNode
 ]
-  ? FnPrim<[Arg], Fn>
+  ? FnPrim<Args, Fn>
   : never;
 
-type MapZip<T extends readonly ASTNode[], U extends readonly PropertyKey[]> = {
+export type MapZip<
+  T extends readonly ASTNode[],
+  U extends readonly PropertyKey[]
+> = {
   [Idx in Exclude<
     keyof T,
     keyof any[]
@@ -102,7 +104,8 @@ export type GetEvaluatedChildren<
     }
   : never;
 
-const input = `map(arr(5,5,5), fn(n, add(n, 1)))` as const;
+const input =
+  `map(arr("hello","world"),fn(s,i,add(tostring(i),":",s)))` as const;
 const lex_result = null as unknown as Lex<typeof input>;
 const parse_result = null as unknown as Parse<typeof lex_result>;
 const eval_result = null as unknown as Evaluate<typeof parse_result>;
diff --git a/src/lang/util/number.ts b/src/lang/util/number.ts
index 132994b..6e4e360 100644
--- a/src/lang/util/number.ts
+++ b/src/lang/util/number.ts
@@ -32,3 +32,6 @@ export type Multiply<M extends number, N extends number> = MultiplyInner<
   M,
   NumberToArray<N>
 >;
+
+export type ExtractNumber<T extends any> =
+  T extends `${infer Inner extends number}` ? Inner : never;
-- 
cgit v1.2.3-70-g09d2