fix: fixed #2130

CHANGELOG.md

@@ -27,7 +27,7 @@
   itself.
 - **#2122** On the Virtual Keyboard, the multiplication key now produces `\cdot` instead
   of `\times`. Use shift to produce `\times`.
-- Improved serialization to ASCIIMath and MathML
+- Improved serialization to ASCIIMath and MathML (**#2130** and others)
 - **#2121** For ASCIIMath and MathML serialization, including phantom closing
   delimiter in the output.
 - Pressing the Action keycap on the virtual keyboard with the shift key pressed

src/editor/atom-to-ascii-math.ts

@@ -128,6 +128,17 @@ const SPECIAL_OPERATORS = {
   // '\\hat': '^'
 };
 
+function joinAsciiMath(xs: string[]): string {
+  let result = '';
+  for (const x of xs) {
+    const last = result[result.length - 1];
+    if (last !== undefined && /\d/.test(last) && /^\d/.test(x)) result += ' ';
+
+    result += x;
+  }
+  return result;
+}
+
 export function atomToAsciiMath(atom: Atom | Atom[] | undefined): string {
   if (!atom) return '';
   if (isArray<Atom>(atom)) {
@@ -148,11 +159,16 @@ export function atomToAsciiMath(atom: Atom | Atom[] | undefined): string {
     }
 
     let i = 0;
-    let result = '';
-    while (atom[i] && atom[i].mode === 'math')
-      result += atomToAsciiMath(atom[i++]);
-
-    return result + atomToAsciiMath(atom.slice(i));
+    const result: string[] = [];
+    while (atom[i] && atom[i].mode === 'math') {
+      let digits = '';
+      while (atom[i] && atom[i].type === 'mord' && /\d/.test(atom[i].value))
+        digits += atom[i++].value;
+      if (digits) result.push(digits);
+      else result.push(atomToAsciiMath(atom[i++]));
+    }
+    result.push(atomToAsciiMath(atom.slice(i)));
+    return joinAsciiMath(result);
   }
 
   if (atom.mode === 'text') return `"${atom.value}"`;
@@ -178,7 +194,7 @@ export function atomToAsciiMath(atom: Atom | Atom[] | undefined): string {
         '\\check': 'check', // non-standard
       }[command];
 
-      result += `${accent ?? ''} ${atomToAsciiMath(atom.body)} `;
+      result = `${accent ?? ''} ${atomToAsciiMath(atom.body)} `;
       break;
 
     case 'first':
@@ -196,7 +212,7 @@ export function atomToAsciiMath(atom: Atom | Atom[] | undefined): string {
       {
         const genfracAtom = atom as GenfracAtom;
         if (genfracAtom.leftDelim || genfracAtom.rightDelim) {
-          result +=
+          result =
             genfracAtom.leftDelim === '.' || !genfracAtom.leftDelim
               ? '{:'
               : genfracAtom.leftDelim;
@@ -294,7 +310,7 @@ export function atomToAsciiMath(atom: Atom | Atom[] | undefined): string {
 
     case 'mopen':
     case 'mclose':
-      result += atom.value;
+      result = atom.value;
       break;
 
     case 'mpunct':

test/math-ascii.test.ts

@@ -56,10 +56,13 @@ describe('ASCII MATH', function () {
   equalASCIIMath('\\Gamma +1', 'Gamma+1');
   equalASCIIMath('\\frac{\\pi }{2\\pi }', '(pi)/(2pi)');
 
-  equalASCIIMath('\\text{if }x>0', '"if "x>0');
+  // Avoid collisions with digits
+  expect(convertLatexToAsciiMath('1^2 3^4')).toBe('1^2 3^4');
+
+  equalASCIIMath('\\text{if }x>0', '"if " x>0');
   equalASCIIMath(
     '\\text{if }x>0\\text{ then }f\\left(x\\right)=x^{2}',
-    '"if "x>0" then "f(x)=x^2'
+    '"if " x>0" then " f(x)=x^2'
   );
   // equalASCIIMath('\\begin{pmatrix}a & b & c\\end{pmatrix}', '((a),(b),(c))');