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/core/common.ts |  18 ++++---
 src/lang/ts-lang/core/eval.ts   | 113 ++++++++++++++++++++++++++++++++++------
 2 files changed, 109 insertions(+), 22 deletions(-)

(limited to 'src/lang/ts-lang/core')

diff --git a/src/lang/ts-lang/core/common.ts b/src/lang/ts-lang/core/common.ts
index fa5cb7c..95a9ad3 100644
--- a/src/lang/ts-lang/core/common.ts
+++ b/src/lang/ts-lang/core/common.ts
@@ -51,16 +51,20 @@ export type ParserCtx = {
 };
 
 export type StackFrame<
-  Bindings extends Record<ASTNode["name"], any> = Record<ASTNode["name"], any>,
-  Parent extends StackFrame | null = any
+  Bindings extends Record<ASTNode["name"], any> = Record<ASTNode["name"], any>
 > = {
   bindings: Bindings;
-  parent: Parent;
 };
 
-export type EmptyStackFrame = StackFrame<{}, null>;
+export type EmptyStackFrame = StackFrame<{}>;
 
-export type WithPushedBindings<
+export type MergeStackFrames<
   OldFrame extends StackFrame,
-  Bindings extends StackFrame["bindings"]
-> = StackFrame<Bindings, OldFrame>;
+  NewFrame extends StackFrame
+> = StackFrame<{
+  [K in
+    | keyof OldFrame["bindings"]
+    | keyof NewFrame["bindings"]]: K extends keyof NewFrame["bindings"]
+    ? NewFrame["bindings"][K]
+    : OldFrame["bindings"][K];
+}>;
diff --git a/src/lang/ts-lang/core/eval.ts b/src/lang/ts-lang/core/eval.ts
index b2fecaa..511ada9 100644
--- a/src/lang/ts-lang/core/eval.ts
+++ b/src/lang/ts-lang/core/eval.ts
@@ -1,14 +1,22 @@
 import {
   BUILTIN_Add,
   BUILTIN_Arr,
+  BUILTIN_Eq,
   BUILTIN_IfElse,
   BUILTIN_Mul,
+  BUILTIN_Sub,
   BUILTIN_ToString,
   SBUILTIN_Call,
   SBUILTIN_Map,
 } from "../builtin";
-import { ToString } from "../util";
-import { ASTNode, EmptyStackFrame, NodeType, StackFrame } from "./common";
+import { NumberToArray, ToString } from "../util";
+import {
+  ASTNode,
+  EmptyStackFrame,
+  MergeStackFrames,
+  NodeType,
+  StackFrame,
+} from "./common";
 
 export type SENTINEL_NO_BUILTIN = "__NO_BUILTIN__";
 export type MapBuiltins<
@@ -25,8 +33,12 @@ export type MapBuiltins<
     ? BUILTIN_Arr<Args>
     : Node["name"] extends "add"
     ? BUILTIN_Add<Args>
+    : Node["name"] extends "sub"
+    ? BUILTIN_Sub<Args>
     : Node["name"] extends "mul"
     ? BUILTIN_Mul<Args>
+    : Node["name"] extends "eq"
+    ? BUILTIN_Eq<Args>
     : Node["name"] extends "?"
     ? BUILTIN_IfElse<Args>
     : SENTINEL_NO_BUILTIN
@@ -38,25 +50,82 @@ export type FindInStack<
   Frame extends StackFrame,
   NameToFind
 > = NameToFind extends keyof Frame["bindings"]
-  ? Frame["bindings"][NameToFind]
-  : Frame["parent"] extends null
-  ? EvalError<`Can't find name "${ToString<NameToFind>}" on the stack`>
-  : FindInStack<Frame["parent"], NameToFind>;
+  ? Frame["bindings"][NameToFind] extends never
+    ? EvalError<`Can't find name "${ToString<NameToFind>}" on the stack`>
+    : Frame["bindings"][NameToFind]
+  : EvalError<`Can't find name "${ToString<NameToFind>}" on the stack`>;
 
 export type FnPrim<
   Args extends readonly ASTNode[] = readonly ASTNode[],
   Fn extends ASTNode = ASTNode
 > = { args: Args; fn: Fn };
 
-export type HandleFn<Node extends ASTNode> = Node["children"] extends [
+export type NamedFnPrim<
+  Args extends readonly ASTNode[],
+  Fn extends ASTNode,
+  Name extends string,
+  CapturedFrame extends StackFrame
+> = { args: Args; fn: Fn; name: Name; frame: CapturedFrame };
+
+type BuildDeepBinding<
+  FnPrim extends NamedFnPrim<any, any, any, any>,
+  Depth extends readonly any[] = [any, any, any, any, any, any, any]
+> = Depth extends []
+  ? FnPrim
+  : BuildDeepBinding<
+      NamedFnPrim<
+        FnPrim["args"],
+        FnPrim["fn"],
+        FnPrim["name"],
+        MergeStackFrames<
+          FnPrim["frame"],
+          StackFrame<{
+            [K in FnPrim["name"]]: NamedFnPrim<
+              FnPrim["args"],
+              FnPrim["fn"],
+              FnPrim["name"],
+              FnPrim["frame"]
+            >;
+          }>
+        >
+      >,
+      Depth extends [infer Head, ...infer Tail] ? Tail : []
+    >;
+
+export type HandleBind<
+  Node extends ASTNode,
+  Frame extends StackFrame
+> = Node["children"] extends [
+  infer Name extends ASTNode,
+  infer Value extends ASTNode
+]
+  ? _Evaluate<Value, Frame> extends infer U
+    ? U extends FnPrim
+      ? NamedFnPrim<
+          U["args"],
+          U["fn"],
+          Name["name"],
+          Frame
+        > extends infer NamedFn
+        ? NamedFn extends NamedFnPrim<infer A, infer F, infer N, any>
+          ? // RECURSION DEPTH LIMIT = 5
+            BuildDeepBinding<NamedFn, NumberToArray<5>>
+          : never
+        : never
+      : U
+    : never
+  : never;
+
+export type HandleFn<
+  Node extends ASTNode,
+  Frame extends StackFrame
+> = Node["children"] extends [
   ...infer Args extends ASTNode[],
   infer Fn extends ASTNode
 ]
   ? FnPrim<Args, Fn>
-  : // error?
-    never;
+  : EvalError<"Invalid args for function call">;
 
-// any[] was propertykey
 export type MapZip<
   Args extends readonly ASTNode[],
   Values extends readonly any[]
@@ -70,10 +139,22 @@ export type MapZip<
 };
 
 export type CallFn<
-  Fn extends FnPrim,
+  Fn,
   Values extends readonly any[],
   Frame extends StackFrame
-> = _Evaluate<Fn["fn"], StackFrame<MapZip<Fn["args"], Values>, Frame>>;
+> = Fn extends NamedFnPrim<
+  infer Args,
+  infer FnBody,
+  infer Name,
+  infer CapturedFrame
+>
+  ? _Evaluate<
+      FnBody,
+      MergeStackFrames<CapturedFrame, StackFrame<MapZip<Args, Values>>>
+    >
+  : Fn extends FnPrim<infer Args, infer FnBody>
+  ? _Evaluate<FnBody, MergeStackFrames<Frame, StackFrame<MapZip<Args, Values>>>>
+  : Fn;
 
 export type _Evaluate<
   Node extends ASTNode,
@@ -81,9 +162,11 @@ export type _Evaluate<
 > = Node["type"] extends NodeType.INT
   ? Node["value"]
   : Node["type"] extends NodeType.EXT
-  ? // special builtin
-    Node["name"] extends "fn"
-    ? HandleFn<Node>
+  ? // special builtins
+    Node["name"] extends "bind"
+    ? HandleBind<Node, Frame>
+    : Node["name"] extends "fn"
+    ? HandleFn<Node, Frame>
     : MapBuiltins<Node, Frame> extends infer BI
     ? BI extends SENTINEL_NO_BUILTIN
       ? FindInStack<Frame, Node["name"]>
-- 
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