mondo: use stepcat for curly braces

packages/mondo/mondo.mjs

@@ -12,10 +12,12 @@ export class MondoParser {
     quotes_single: /^'(.*?)'/,
     open_list: /^\(/,
     close_list: /^\)/,
-    open_cat: /^</,
+    open_cat: /^</, // todo: rename angle
     close_cat: /^>/,
-    open_seq: /^\[/,
+    open_seq: /^\[/, // todo: rename square
     close_seq: /^\]/,
+    open_curly: /^\{/,
+    close_curly: /^\}/,
     number: /^-?[0-9]*\.?[0-9]+/, // before pipe!
     op: /^[*/:!@%]|^\.{2}/, // * / : ! @ % ..
     pipe: /^\./,
@@ -93,6 +95,9 @@ export class MondoParser {
     if (next === 'open_seq') {
       return this.parse_seq();
     }
+    if (next === 'open_curly') {
+      return this.parse_curly();
+    }
     return this.consume(next);
   }
   desugar_children(children) {
@@ -256,6 +261,12 @@ export class MondoParser {
     children = this.desugar(children, 'seq');
     return { type: 'list', children };
   }
+  parse_curly() {
+    let children = this.parse_pair('open_curly', 'close_curly');
+    children = [{ type: 'plain', value: 'curly' }, ...children];
+    children = this.desugar(children, 'curly');
+    return { type: 'list', children };
+  }
   consume(type) {
     // shift removes first element and returns it
     const token = this.tokens.shift();

packages/mondough/mondough.mjs

@@ -1,4 +1,4 @@
-import { strudelScope, reify, fast, slow, seq } from '@strudel/core';
+import { strudelScope, reify, fast, slow, seq, stepcat } from '@strudel/core';
 import { registerLanguage } from '@strudel/transpiler';
 import { MondoRunner } from '../mondo/mondo.mjs';
 
@@ -18,18 +18,15 @@ strudelScope.leaf = (token, scope) => {
   }
   return reify(value).withLoc(from, to);
 };
+strudelScope.curly = stepcat;
+strudelScope.seq = (...args) => stepcat(...args).setSteps(1);
+strudelScope.cat = (...args) => stepcat(...args).pace(1);
 
 strudelScope.call = (fn, args, name) => {
   const [pat, ...rest] = args;
-  if (!['seq', 'cat', 'stack', ':', '..', '!', '@', '%'].includes(name)) {
+  if (!['seq', 'cat', 'stack', 'curly', ':', '..', '!', '@', '%'].includes(name)) {
     args = [...rest, pat];
   }
-  if (name === 'seq') {
-    return stepcat(...args).setSteps(1);
-  }
-  if (name === 'cat') {
-    return stepcat(...args).pace(1);
-  }
   return fn(...args);
 };