From 8b610f2bcfc223333254ce9679730c42dce6d26e Mon Sep 17 00:00:00 2001
From: Kai Stevenson <kai@kaistevenson.com>
Date: Mon, 3 Nov 2025 23:41:31 -0800
Subject: add createFn

---
 src/lang/js-lang/core/eval.ts | 83 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 src/lang/js-lang/core/eval.ts

(limited to 'src/lang/js-lang/core/eval.ts')

diff --git a/src/lang/js-lang/core/eval.ts b/src/lang/js-lang/core/eval.ts
new file mode 100644
index 0000000..60a2059
--- /dev/null
+++ b/src/lang/js-lang/core/eval.ts
@@ -0,0 +1,83 @@
+import {
+  ASTNode,
+  StackFrame,
+  Evaluate,
+  EmptyStackFrame,
+  NodeType,
+  FnPrim,
+  SENTINEL_NO_BUILTIN,
+} from "../../ts-lang";
+import { nameToBUILTIN, nameToSBUILTIN, V_SBUILTIN_Map } from "../builtin";
+
+const V_SENTINEL_NO_BUILTIN: SENTINEL_NO_BUILTIN = "__NO_BUILTIN__";
+
+const mapBuiltins = (node: ASTNode, frame: StackFrame): any => {
+  if (node.name in nameToSBUILTIN) {
+    return nameToSBUILTIN[node.name](node, frame);
+  }
+  if (node.name in nameToBUILTIN) {
+    return nameToBUILTIN[node.name](getEvaluatedChildren(node, frame));
+  }
+
+  return V_SENTINEL_NO_BUILTIN;
+};
+
+const findInStack = (frame: StackFrame, nameToFind: string) => {
+  if (nameToFind in frame.bindings) {
+    return frame.bindings[nameToFind];
+  }
+
+  if (!frame.parent) {
+    throw new Error(`Can't find name ${nameToFind} on the stack`);
+  }
+
+  return findInStack(frame.parent, nameToFind);
+};
+
+const handleFn = (node: ASTNode): FnPrim => {
+  const fn = node.children[node.children.length - 1];
+
+  return {
+    args: node.children.slice(0, node.children.length - 1),
+    fn,
+  };
+};
+
+const mapZip = (args: ASTNode[], values: any[]) =>
+  Object.fromEntries(args.map(({ name }, i) => [name, values[i]]));
+
+export const callFn = (fn: FnPrim, values: any[], frame: StackFrame) =>
+  _evaluate(fn.fn, {
+    bindings: mapZip(fn.args as ASTNode[], values),
+    parent: frame,
+  });
+
+export const _evaluate = (node: ASTNode, frame: StackFrame) => {
+  if (node.type === NodeType.INT) {
+    return node.value;
+  }
+
+  if (node.type === NodeType.EXT) {
+    if (node.name === "fn") {
+      return handleFn(node);
+    }
+
+    const builtinResult = mapBuiltins(node, frame);
+    if (builtinResult !== V_SENTINEL_NO_BUILTIN) {
+      return builtinResult;
+    }
+
+    return findInStack(frame, node.name);
+  }
+
+  throw new Error(`Unhandled node type ${node.type}`);
+};
+
+export const getEvaluatedChildren = (node: ASTNode, frame: StackFrame) =>
+  node.children.map((child) => _evaluate(child, frame));
+
+export const emptyStackFrame: EmptyStackFrame = { bindings: {}, parent: null };
+
+export const evaluate = <const Node extends ASTNode>(
+  node: Node
+): Evaluate<Node> => _evaluate(node, emptyStackFrame) as Evaluate<Node>;
-- 
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