fix: enhance LaTeX parsing for limits with postfix operators

Author: arnog

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 #### Fixed
 
+- **LaTeX parsing: `\lim` with postfix operators** — `\lim_{x\to 0}\left(x\right)^x`
+  now correctly parses as `Limit(x^x)` instead of `Power(Limit(x), x)`. The
+  `\lim` parser was using `parseArguments('implicit')` which stripped the
+  delimiters and left the `^x` unconsumed; it now uses `parseExpression` so
+  postfix operators are included in the limit body.
+
 - **LaTeX parsing: style, size, and color switch commands** — `\displaystyle`,
   `\textstyle`, `\scriptstyle`, `\scriptscriptstyle`, `\tiny`..`\Huge` (10 size
   commands), and `\color{...}` were silently discarded during parsing. They now

src/compute-engine/latex-syntax/dictionary/definitions-arithmetic.ts

@@ -1319,11 +1319,16 @@ export const DEFINITIONS_ARITHMETIC: LatexDictionary = [
       if (!parser.match('_')) return null;
       const base = parser.parseGroup();
       if (operator(base) !== 'To') return null;
-      const expr = parser.parseArguments('implicit');
+      // Use parseExpression instead of parseArguments('implicit') so that
+      // postfix operators like ^x are included in the limit body.
+      // e.g. \lim_{x\to 0}\left(x\right)^x  →  Limit(x^x) not Limit(x)^x
+      const expr = parser.parseExpression({
+        minPrec: MULTIPLICATION_PRECEDENCE,
+      });
       if (!expr) return null;
       return [
         'Limit',
-        ['Function', expr[0], operand(base, 1)],
+        ['Function', expr, operand(base, 1)],
         operand(base, 2),
       ] as MathJsonExpression;
     },

test/playground.ts

@@ -18,8 +18,7 @@ import {
 const ce = new ComputeEngine();
 const engine = ce;
 
-console.log(parse('x + 2 = \\square').json);
-console.log(parse('x + 2 = \\placeholder').json);
+console.log(parse('\\lim_{x\\to 0}\\left(x\\right)^x').toMathJson());
 
 parse('[5,7)');
 // -> ok, `["Interval", 5, ["Open", 7]]`