From 3505732afad89870286d2c0083887375c62e6b44 Mon Sep 17 00:00:00 2001
From: Felix Roos <flix91@gmail.com>
Date: Thu, 20 Mar 2025 09:34:47 +0100
Subject: [PATCH] mondo: add .. operator

---
 packages/mondo/mondo.mjs           |  2 +-
 packages/mondo/test/mondo.test.mjs |  1 +
 packages/mondough/mondough.mjs     | 11 ++++++++++-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/packages/mondo/mondo.mjs b/packages/mondo/mondo.mjs
index 5997feb40..70c58aa6d 100644
--- a/packages/mondo/mondo.mjs
+++ b/packages/mondo/mondo.mjs
@@ -17,9 +17,9 @@ export class MondoParser {
     open_seq: /^\[/,
     close_seq: /^\]/,
     number: /^-?[0-9]*\.?[0-9]+/, // before pipe!
+    op: /^[*\/:]|^\.{2}/, // * / : ..
     pipe: /^\./,
     stack: /^[,$]/,
-    op: /^[*/:]/,
     plain: /^[a-zA-Z0-9-~_^]+/,
   };
   // matches next token
diff --git a/packages/mondo/test/mondo.test.mjs b/packages/mondo/test/mondo.test.mjs
index e21ec75b0..aadbafbeb 100644
--- a/packages/mondo/test/mondo.test.mjs
+++ b/packages/mondo/test/mondo.test.mjs
@@ -102,6 +102,7 @@ describe('mondo sugar', () => {
   it('should desugar x:y', () => expect(desguar('x:y')).toEqual('(: x y)'));
   it('should desugar x:y:z', () => expect(desguar('x:y:z')).toEqual('(: (: x y) z)'));
   it('should desugar x:y*x', () => expect(desguar('bd:0*2')).toEqual('(* (: bd 0) 2)'));
+  it('should desugar a..b', () => expect(desguar('0..2')).toEqual('(.. 0 2)'));
 
   it('should desugar README example', () =>
     expect(desguar('s [bd hh*2 cp.(crush 4) <mt ht lt>] . speed .8')).toEqual(
diff --git a/packages/mondough/mondough.mjs b/packages/mondough/mondough.mjs
index 33e0116df..e69ea0994 100644
--- a/packages/mondough/mondough.mjs
+++ b/packages/mondough/mondough.mjs
@@ -21,7 +21,7 @@ strudelScope.leaf = (token, scope) => {
 
 strudelScope.call = (fn, args, name) => {
   const [pat, ...rest] = args;
-  if (!['seq', 'cat', 'stack', ':'].includes(name)) {
+  if (!['seq', 'cat', 'stack', ':', '..'].includes(name)) {
     args = [...rest, pat];
   }
   return fn(...args);
@@ -30,9 +30,18 @@ strudelScope.call = (fn, args, name) => {
 strudelScope['*'] = fast;
 strudelScope['/'] = slow;
 
+// : operator
 const tail = (pat, friend) => pat.fmap((a) => (b) => (Array.isArray(a) ? [...a, b] : [a, b])).appLeft(friend);
 strudelScope[':'] = tail;
 
+// .. operator
+const arrayRange = (start, stop, step = 1) =>
+  Array.from({ length: Math.abs(stop - start) / step + 1 }, (_, index) =>
+    start < stop ? start + index * step : start - index * step,
+  );
+const range = (min, max) => min.squeezeBind((a) => max.bind((b) => seq(...arrayRange(a, b))));
+strudelScope['..'] = range;
+
 export function mondo(code, offset = 0) {
   if (Array.isArray(code)) {
     code = code.join('');