support : in mondo

packages/mondo/mondo.mjs

@@ -20,6 +20,7 @@ export class MondoParser {
     pipe: /^\./,
     stack: /^[,$]/,
     op: /^[*/]/,
+    tail: /^:/,
     plain: /^[a-zA-Z0-9-~_^]+/,
   };
   // matches next token
@@ -96,6 +97,7 @@ export class MondoParser {
     return this.consume(next);
   }
   desugar_children(children) {
+    children = this.resolve_tails(children);
     children = this.resolve_ops(children);
     children = this.resolve_pipes(children);
     return children;
@@ -144,6 +146,35 @@ export class MondoParser {
     });
     return [{ type: 'plain', value: 'stack' }, ...args];
   }
+  resolve_tails(children) {
+    while (true) {
+      let opIndex = children.findIndex((child) => child.type === 'tail');
+      if (opIndex === -1) break;
+      const op = { type: 'plain', value: children[opIndex].value };
+      if (opIndex === children.length - 1) {
+        throw new Error(`cannot use operator as last child.`);
+      }
+      if (opIndex === 0) {
+        // regular function call (assuming each operator exists as function)
+        children[opIndex] = op;
+        continue;
+      }
+      const left = children[opIndex - 1];
+      const right = children[opIndex + 1];
+
+      // convert infix to prefix notation
+      const call = { type: 'list', children: [op, left, right] };
+
+      // insert call while keeping other siblings
+      children = [...children.slice(0, opIndex - 1), call, ...children.slice(opIndex + 2)];
+      // unwrap double list.. e.g. (s jazz) * 2
+      if (children.length === 1) {
+        // there might be a cleaner solution
+        children = children[0].children;
+      }
+    }
+    return children;
+  }
   resolve_ops(children) {
     while (true) {
       let opIndex = children.findIndex((child) => child.type === 'op');

packages/mondo/test/mondo.test.mjs

@@ -99,6 +99,8 @@ describe('mondo sugar', () => {
   it('should desugar , ()', () => expect(desguar('(s bd, s cp)')).toEqual('(stack (s bd) (s cp))'));
   it('should desugar * /', () => expect(desguar('[a b*2 c d/3 e]')).toEqual('(seq a (* b 2) c (/ d 3) e)'));
   it('should desugar []*x', () => expect(desguar('[a [b c]*3]')).toEqual('(seq a (* (seq b c) 3))'));
+  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 README example', () =>
     expect(desguar('s [bd hh*2 cp.(crush 4) <mt ht lt>] . speed .8')).toEqual(

packages/mondough/mondough.mjs

@@ -17,7 +17,7 @@ strudelScope.leaf = (token) => {
 
 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);
@@ -26,6 +26,9 @@ strudelScope.call = (fn, args, name) => {
 strudelScope['*'] = fast;
 strudelScope['/'] = slow;
 
+const tail = (pat, friend) => pat.fmap((a) => (b) => (Array.isArray(a) ? [...a, b] : [a, b])).appLeft(friend);
+strudelScope[':'] = tail;
+
 export function mondo(code, offset = 0) {
   if (Array.isArray(code)) {
     code = code.join('');