# Parsing and Serializing LaTeX

The CortexJS Compute Engine manipulates MathJSON expressions. It can also convert LaTeX strings to MathJSON expressions (parsing) and output MathJSON expressions as LaTeX string (serializing).

To transform LaTeX to MathJSON, use the parse() function.

To transform MathJSON to LaTeX, use the serialize() function.

import { parse, serialize } from '@cortex-js/compute-engine';

const expr = parse('\\frac{\\pi}{2}');
console.log(expr);
// ➔ ["Divide", "Pi", 2]

const latex = serialize(expr);
console.log(latex);
// ➔ \frac{\pi}{2}


The behavior of parse() and serialize() can be customized by passing an optional argument:

import {  serialize } from '@cortex-js/compute-engine'

console.log(serialize(1/3, {
precision: 3,
decimalMarker: ","
}););
// ➔ 0,333


To customize the LaTeX syntax, including defining the vocabulary and syntax, create an instance of LatexSyntax.

import { LatexSyntax } from '@cortex-js/compute-engine';
const latexSyntax = new LatexSyntax();
const expr = latexSyntax.parse('\\frac{\\pi}{2}');
console.log(expr);
const latex = latexSyntax.serialize(expr);
console.log(latex);


The LatexSyntax constructor can be passed some options to customize the parsing and serializing, as well as dictionaries defining the syntax and vocabulary.

To change the LaTeX syntax options after a LatexSyntax instance has been created, change the options property.

The LatexSyntax class has an options property with the following keys.

### Number Formatting Options

Option
precision
positiveInfinity
negativeInfinity
notANumber
decimalMarker The string separating the whole portion of a number from the fractional portion, i.e. the ‘.’ in 3.1415.
groupSeparator The separator between groups of digits, used to improve readability of numbers with many digits
exponentProduct
beginExponentMarker
endExponentMarker
notation engineering auto scientific
truncationMarker
beginRepeatingDigits
endRepeatingDigits
imaginaryNumber

### Serialization Options

Option
invisibleMultiply LaTeX string used to render an invisible multiply, e.g. in 2x. Leave it empty to join the adjacent terms, or use \cdot to insert a \cdot operator between them, i.e. 2\cdot x
invisiblePlus LaTeX string used for an invisible plus, e.g. in ‘1 3/4’. Leave it empty to join the main number and the fraction, i.e. render it as 1\frac{3}{4}, or use + to insert a + operator between them, i.e. 1+\frac{3}{4}
multiply LaTeX string used for an explicit multiply operator: for example \times or \cdot

### Parsing Options

Option
invisibleOperator If a symbol follows a number, consider them separated by this invisible operator. Default: Multiply
skipSpace If true, ignore space characters
parseArgumentsOfUnknownLatexCommands When an unknown latex command is encountered, attempt to parse any arguments it may have.
For example, \foo{x+1} would produce ["\foo", ["Add", "x", 1]] if this property is true, ["LatexSymbols", "\foo", "<{>", "x", "+", 1, "<{>"] otherwise.
parseNumbers When a number is encountered, parse it.
Otherwise, return each token making up the number (minus sign, digits, decimal separator, etc…)
invisiblePlusOperator If this setting is not empty, when a number is immediately followed by a fraction, assume that the fraction should be added to the number, that is that there is an invisible plus operator between the two.
For example with 2\frac{3}{4}
• when invisiblePlusOperator is "Add" : ["Add", 2, ["Divide", 3, 4]]
• when invisiblePlusOperator is "": ["Multiply", 2, ["Divide", 3, 4]]
preserveLatex If true, the expression will be decorated with the LaTeX fragments corresponding to each elements of the expression

### Example: Parsing Raw LaTeX

The configuration below will result in parsing a LaTeX string as a sequence of LaTeX tokens, without any interpration. It uses no dictionary (since only tokens are returned) and set the options to avoid modifying the raw stream of LaTeX tokens.

const rawLatex = new LatexSyntax({
parseArgumentsOfUnknownLatexCommands: false,
parseUnknownToken: () => 'symbol',
invisibleOperator: '',
invisiblePlusOperator: '',
dictionary: [],
skipSpace: false,
});
const expr = rawLatex.parse('\\frac{\\pi}{2}');
console.log(expr);
// ➔ ["LatexTokens", "'\frac'", "'<{>'", "'\pi'", "'<}>'", "'<{>'",  2, "'<}>'"]