feat: added \mleft...\mright support, parse \color

Author: arnog

CHANGELOG.md

@@ -1,5 +1,19 @@
 ### [Unreleased]
 
+- **Parse `\mleft`/`\mright` delimiters**: These alternative delimiters from the
+  `mleftright` LaTeX package are now recognized and behave identically to
+  `\left`/`\right`.
+
+- **Parse `\color` in math mode**: The `\color{...}` command is now recognized
+  in math mode. The color argument is consumed and discarded, allowing the
+  subsequent expression to parse normally. Previously, `\color{red}3` produced
+  an `unexpected-command` error.
+
+- **Parse `:` and `\colon` as infix operators**: A bare `:` or `\colon` outside
+  of quantifier contexts now parses as a `Colon` infix operator, useful for type
+  annotations and mapping notation (e.g., `f:[a,b]\to\R`). The `:=` assignment
+  operator and quantifier colon syntax are unaffected.
+
 - **`expand()` now returns the input expression instead of `null`**: The
   `expand()` free function and the internal `expand()` / `expandAll()` functions
   now return the original expression when no expansion is possible, instead of

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

@@ -366,6 +366,30 @@ export const DEFINITIONS_CORE: LatexDictionary = [
     parse: parseAssign,
   },
 
+  // General colon operator (type annotation, mapping notation)
+  // Precedence below assignment (260) so `:=` takes priority,
+  // and below arrows (270) so `f: A \to B` parses as `Colon(f, To(A, B))`
+  {
+    name: 'Colon',
+    latexTrigger: ':',
+    kind: 'infix',
+    associativity: 'right',
+    precedence: 250,
+    serialize: (serializer: Serializer, expr: MathJsonExpression): string =>
+      joinLatex([
+        serializer.serialize(operand(expr, 1)),
+        '\\colon',
+        serializer.serialize(operand(expr, 2)),
+      ]),
+  },
+  {
+    latexTrigger: '\\colon',
+    kind: 'infix',
+    associativity: 'right',
+    precedence: 250,
+    parse: 'Colon',
+  },
+
   {
     name: 'BaseForm',
     serialize: (serializer, expr) => {

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

@@ -552,7 +552,15 @@ function parseQuantifier(
     // 2. If we didn't find a standalone symbol, we look for a condition
     //
     parser.index = index;
-    const condition = parser.parseExpression(terminator);
+    // Stop at colon separators so the quantifier can consume them
+    const condTerminator = {
+      ...terminator,
+      condition: (p: Parser) =>
+        p.peek === ':' ||
+        p.peek === '\\colon' ||
+        (terminator.condition?.(p) ?? false),
+    };
+    const condition = parser.parseExpression(condTerminator);
     if (condition === null) return null;
 
     // Either a separator or a parenthesis

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

@@ -278,6 +278,14 @@ export const DEFINITIONS_OTHERS: LatexDictionary = [
     latexTrigger: ['\\scriptscriptstyle'],
     parse: () => 'Nothing', // @todo: parse as ['Annotated'...]
   },
+  {
+    latexTrigger: ['\\color'],
+    parse: (parser: Parser) => {
+      // Consume the {color} argument and discard it
+      parser.parseGroup();
+      return 'Nothing';
+    },
+  },
 
   {
     latexTrigger: ['\\tiny'],

src/compute-engine/latex-syntax/parse.ts

@@ -99,6 +99,7 @@ const OPEN_DELIMITER_PREFIX = {
   '\\bigg': '\\bigg',
   '\\Bigg': '\\Bigg',
   '\\mathopen': '\\mathclose',
+  '\\mleft': '\\mright',
 };
 
 /** Commands that can be used with a middle delimiter */
@@ -1032,6 +1033,7 @@ export class _Parser implements Parser {
       ...'!"#$%&(),/;:?@[]\\`|~'.split(''),
       '\\left',
       '\\bigl',
+      '\\mleft',
     ];
     if (excluding.includes(this.peek)) return null;
 

test/compute-engine/latex-syntax/stefnotch.test.ts

@@ -46,25 +46,28 @@ describe('STEFNOTCH #10', () => {
   });
 
   test('4/ \\color{red}3', () => {
-    expect(parse('\\color{red}3')).toMatchInlineSnapshot(`
-      [
-        "Tuple",
-        ["Error", "unexpected-command", ["LatexString", "\\color"]],
-        "r",
-        "ExponentialE",
-        "d",
-        3
-      ]
-    `);
+    expect(parse('\\color{red}3')).toMatchInlineSnapshot(`3`);
+  });
+
+  test('4b/ \\color{blue}{x+y}', () => {
+    expect(parse('\\color{blue}{x+y}')).toMatchInlineSnapshot(
+      `["Add", "x", "y"]`
+    );
   });
 
   test('5/ \\ln(3)', () => {
     expect(parse('\\ln(3)')).toMatchInlineSnapshot(`["Ln", 3]`);
   });
 
-  test('6/ f:[a,b]\\to R', () => {
-    expect(parse('f:[a,b]\\to R ')).toMatchInlineSnapshot(
-      `["Sequence", "f", ["Error", ["ErrorCode", "unexpected-token", ":"]]]`
+  test('6/ f:[a,b]\\to\\R', () => {
+    expect(parse('f:[a,b]\\to\\R')).toMatchInlineSnapshot(
+      `["Colon", "f", ["To", ["List", "a", "b"], "RealNumbers"]]`
+    );
+  });
+
+  test('6b/ x:\\R', () => {
+    expect(parse('x:\\R')).toMatchInlineSnapshot(
+      `["Colon", "x", "RealNumbers"]`
     );
   });
 
@@ -74,6 +77,10 @@ describe('STEFNOTCH #10', () => {
     );
   });
 
+  test('8a/ \\mleft(x\\mright) parses like \\left(x\\right)', () => {
+    expect(parse('\\mleft(x\\mright)')).toMatchInlineSnapshot(`x`);
+  });
+
   test('8/ \\begin{cases} 3 & x < 5 \\\\ 7 & \\text{else} \\end{cases}', () => {
     expect(
       parse('\\begin{cases} 3 & x < 5 \\\\ 7 & \\text{else} \\end{cases}')