From c44a6858ffa80c8ab4bde7d5bf355ed8571b244e Mon Sep 17 00:00:00 2001
From: Dustin Swan <dustin@dustinswan.com>
Date: Sun, 1 Feb 2026 16:46:18 -0700
Subject: [PATCH] interpreting record update, and > (func application pipe
 thing). cleaning up main.ts test code

---
 src/interpreter.ts | 48 +++++++++++++++++++++++++++++++++++++---------
 src/main.ts        | 46 ++++++++++++++------------------------------
 src/parser.ts      |  1 -
 3 files changed, 53 insertions(+), 42 deletions(-)

diff --git a/src/interpreter.ts b/src/interpreter.ts
index 6cfc171..2706f25 100644
--- a/src/interpreter.ts
+++ b/src/interpreter.ts
@@ -7,11 +7,14 @@ export function evaluate(ast: AST, env: Env): Value {
         case 'literal':
             return ast.value;
 
-        case 'variable':
+        case 'variable': {
             const val = env.get(ast.name);
+
             if (val === undefined)
                 throw new Error(`Unknown variable: ${ast.name}`);
+
             return val;
+        }
 
         case 'list':
             return {
@@ -28,7 +31,7 @@ export function evaluate(ast: AST, env: Env): Value {
 
             return { kind: 'record', fields };
 
-        case 'record-access':
+        case 'record-access': {
             const record = evaluate(ast.record, env);
 
             if (record.kind !== 'record')
@@ -41,6 +44,22 @@ export function evaluate(ast: AST, env: Env): Value {
             }
 
             return value;
+        }
+
+        case 'record-update': {
+            const record = evaluate(ast.record, env);
+
+            if (record.kind !== 'record')
+                throw new Error('Not a record');
+
+            const newFields: { [key: string]: Value } = { ...record.fields };
+
+            for (const [field, expr] of Object.entries(ast.updates)) {
+                newFields[field] = evaluate(expr, env);
+            }
+
+            return { kind: 'record', fields: newFields };
+        }
 
         case 'constructor':
             return {
@@ -49,10 +68,11 @@ export function evaluate(ast: AST, env: Env): Value {
                 args: [] // TODO: constructors args
             };
 
-        case 'let':
-            const val2 = evaluate(ast.value, env);
-            const newEnv = new Map(env).set(ast.name, val2);
+        case 'let': {
+            const val = evaluate(ast.value, env);
+            const newEnv = new Map(env).set(ast.name, val);
             return evaluate(ast.body, newEnv);
+        }
 
         case 'lambda':
             return {
@@ -62,7 +82,7 @@ export function evaluate(ast: AST, env: Env): Value {
                 env
             }
 
-        case 'apply':
+        case 'apply': {
             // Operators
             if (ast.func.kind === 'variable') {
                 const name = ast.func.name;
@@ -114,10 +134,10 @@ export function evaluate(ast: AST, env: Env): Value {
             }
 
             return evaluate(func.body, callEnv);
+        }
 
         default:
             throw new Error('Syntax Error');
-
     }
 }
 
@@ -155,8 +175,18 @@ function evaluateBuiltIn(op: string, left: Value, right: Value): Value {
         return evaluateBinaryOp(op, left, right);
     }
 
-    if (op === '>')
-        throw new Error('TODO Not implemented yet');
+    if (op === '>') {
+        // x > f means f(x)
+        if (right.kind !== 'closure')
+            throw new Error('Right side of > must be a function');
+
+        if (right.params.length !== 1)
+            throw new Error('Pipe only works with 1-arg functions for now..');
+
+        const callEnv = new Map(right.env);
+        callEnv.set(right.params[0], left);
+        return evaluate(right.body, callEnv);
+    }
 
     if (op === '&')
         throw new Error('TODO Not implemented yet');
diff --git a/src/main.ts b/src/main.ts
index 9aee4b3..653f4cf 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1,39 +1,21 @@
 import { evaluate } from './interpreter'
-// import type { AST } from './ast'
 import type { Env } from './env'
 import { tokenize } from './lexer'
 import { Parser } from './parser'
 import { prettyPrint } from './ast';
 
-// const env: Env = new Map();
+function e(str: string) {
+    const tokens = tokenize(str);
+    const p = new Parser(tokens);
+    const ast = p.parse();
+    const env: Env = new Map();
+    console.log(str, tokens, prettyPrint(ast), evaluate(ast, env));
+}
 
-// const res = evaluate(ast, env);
-
-// console.log(res);
-
-const str = `
-# This is a comment
-double = x \\ x * 2
-read_line! : Unit \\ String
-`;
-console.log(tokenize(str));
-
-// const tokens = tokenize("x");
-// const p = new Parser(tokens);
-// console.log(p.parse());
-
-// const tokens2 = tokenize("let x = (y) => 5 + y in x(3)");
-// const tokens2 = tokenize("let x = 5 in x * 4");
-// const tokens2 = tokenize("(x, y) => x + y");
-// const tokens2 = tokenize('point { x = 3 }');
-// const tokens2 = tokenize('add1 = (x \\ x + 1); add1 3');
-// const tokens2 = tokenize('sum = x y \\ x + y; sum 5 3');
-// const tokens2 = tokenize('[1, 2, 3]');
-// const tokens2 = tokenize('c = 5; { a = 3, b = c }');
-const tokens2 = tokenize('rec = { a = 3, b = 5 }; rec.a');
-const p2 = new Parser(tokens2);
-const ast3 = p2.parse();
-console.log(ast3);
-console.log(prettyPrint(ast3));
-const env3: Env = new Map();
-console.log(evaluate(ast3, env3));
+e('add1 = (x \\ x + 1); add1 3');
+e('sum = x y \\ x + y; sum 5 3');
+e('[1, 2, 3]');
+e('c = 5; { a = 3, b = c }');
+e('rec = { a = 3, b = 5 }; rec.a');
+e('rec = { a = 3, b = 5 }; rec{ a = 10 }');
+e('add1 = (x \\ x + 1); 3 > add1');
diff --git a/src/parser.ts b/src/parser.ts
index 01a81ac..a210614 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -7,7 +7,6 @@ export class Parser {
 
     constructor(tokens: Token[]) {
         this.tokens = tokens;
-        console.log("tokens", tokens);
     }
 
     private current(): Token {