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latex.ts
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latex.ts
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// Copyright (c) Jupyter Development Team.
// Distributed under the terms of the Modified BSD License.
// Some magic for deferring mathematical expressions to MathJax
// by hiding them from the Markdown parser.
// Some of the code here is adapted with permission from Davide Cervone
// under the terms of the Apache2 license governing the MathJax project.
// Other minor modifications are also due to StackExchange and are used with
// permission.
const inline = '$'; // the inline math delimiter
// MATHSPLIT contains the pattern for math delimiters and special symbols
// needed for searching for math in the text input.
const MATHSPLIT = /(\$\$?|\\(?:begin|end)\{[a-z]*\*?\}|\\[\\{}$]|[{}]|(?:\n\s*)+|@@\d+@@)/i;
// A module-level initialization flag.
let initialized = false;
/**
* Break up the text into its component parts and search
* through them for math delimiters, braces, linebreaks, etc.
* Math delimiters must match and braces must balance.
* Don't allow math to pass through a double linebreak
* (which will be a paragraph).
*/
export
function removeMath(text: string): { text: string, math: string[] } {
let math: string[] = []; // stores math strings for later
let start: number;
let end: string;
let last: number;
let braces: number;
let deTilde: (text: string) => string;
if (!initialized) {
init();
initialized = true;
}
// Except for extreme edge cases, this should catch precisely those pieces of the markdown
// source that will later be turned into code spans. While MathJax will not TeXify code spans,
// we still have to consider them at this point; the following issue has happened several times:
//
// `$foo` and `$bar` are variables. --> <code>$foo ` and `$bar</code> are variables.
let hasCodeSpans = /`/.test(text);
if (hasCodeSpans) {
text = text.replace(/~/g, '~T').replace(/(^|[^\\])(`+)([^\n]*?[^`\n])\2(?!`)/gm, (wholematch) => wholematch.replace(/\$/g, '~D'));
deTilde = (text: string) => {
return text.replace(/~([TD])/g,
(wholematch, character) => (character === 'T') ? '~' : '$');
};
} else {
deTilde = (text: string) => { return text; };
}
let blocks = text.replace(/\r\n?/g, '\n').split(MATHSPLIT);
for (let i = 1, m = blocks.length; i < m; i += 2) {
let block = blocks[i];
if (block.charAt(0) === '@') {
//
// Things that look like our math markers will get
// stored and then retrieved along with the math.
//
blocks[i] = '@@' + math.length + '@@';
math.push(block);
}
else if (start) {
//
// If we are in math, look for the end delimiter,
// but don't go past double line breaks, and
// and balance braces within the math.
//
if (block === end) {
if (braces) {
last = i;
}
else {
blocks = processMath(start, i, deTilde, math, blocks);
start = null;
end = null;
last = null;
}
}
else if (block.match(/\n.*\n/)) {
if (last) {
i = last;
blocks = processMath(start, i, deTilde, math, blocks);
}
start = null;
end = null;
last = null;
braces = 0;
}
else if (block === '{') {
braces++;
}
else if (block === '}' && braces) {
braces--;
}
}
else {
//
// Look for math start delimiters and when
// found, set up the end delimiter.
//
if (block === inline || block === '$$') {
start = i;
end = block;
braces = 0;
}
else if (block.substr(1, 5) === 'begin') {
start = i;
end = '\\end' + block.substr(6);
braces = 0;
}
}
}
if (last) {
blocks = processMath(start, last, deTilde, math, blocks);
start = null;
end = null;
last = null;
}
return { text: deTilde(blocks.join('')), math };
};
/**
* Put back the math strings that were saved,
* and clear the math array (no need to keep it around).
*/
export
function replaceMath(text: string, math: string[]): string {
text = text.replace(/@@(\d+)@@/g, (match, n) => math[n]);
return text;
};
/**
* Typeset the math in a node.
*/
export
function typeset(node: HTMLElement): void {
if (!initialized) {
init();
initialized = true;
}
if ((window as any).MathJax) {
MathJax.Hub.Queue(['Typeset', MathJax.Hub, node]);
}
}
/**
* Initialize latex handling.
*/
function init() {
if (!(window as any).MathJax) {
return;
}
MathJax.Hub.Config({
tex2jax: {
inlineMath: [ ['$', '$'], ['\\(', '\\)'] ],
displayMath: [ ['$$', '$$'], ['\\[', '\\]'] ],
processEscapes: true,
processEnvironments: true
},
// Center justify equations in code and markdown cells. Elsewhere
// we use CSS to left justify single line equations in code cells.
displayAlign: 'center',
CommonHTML: {
linebreaks: { automatic: true }
},
'HTML-CSS': {
availableFonts: [],
imageFont: null,
preferredFont: null,
webFont: 'STIX-Web',
styles: {'.MathJax_Display': {'margin': 0}},
linebreaks: { automatic: true }
},
});
MathJax.Hub.Configured();
}
/**
* Process math blocks.
*
* The math is in blocks i through j, so
* collect it into one block and clear the others.
* Replace &, <, and > by named entities.
* For IE, put <br> at the ends of comments since IE removes \n.
* Clear the current math positions and store the index of the
* math, then push the math string onto the storage array.
* The preProcess function is called on all blocks if it has been passed in
*/
function processMath(i: number, j: number, preProcess: (input: string) => string, math: string[], blocks: string[]): string[] {
let block = blocks.slice(i, j + 1).join('').replace(/&/g, '&') // use HTML entity for &
.replace(/</g, '<') // use HTML entity for <
.replace(/>/g, '>') // use HTML entity for >
;
if (navigator && navigator.appName === 'Microsoft Internet Explorer') {
block = block.replace(/(%[^\n]*)\n/g, '$1<br/>\n');
}
while (j > i) {
blocks[j] = '';
j--;
}
blocks[i] = '@@' + math.length + '@@'; // replace the current block text with a unique tag to find later
if (preProcess) {
block = preProcess(block);
}
math.push(block);
return blocks;
};