here to learn
example = (await fetch(
"https://gist.githubusercontent.com/bryangingechen/e340aa91244e730798a39156f371e89a/raw/46d1d5caf0cde719293414cc04ff56f892c37529/system_of_equations.md"
)).text()
example2 = removeMath(example, '$')
example2.text
example2.math
replaceMath(example2.text, example2.math)
SPLIT = /(\$\$?|\\(?:begin|end)\{[a-z]*\*?\}|\\[\\{}$]|[{}]|(?:\n\s*)+|@@\d+@@|`+)/i
capturingStringSplit = function(str, regex) {
return str.split(regex);
}
//
// 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).
// Handle backticks (don't do math inside them)
//
function removeMath(text, inline) {
//
// 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.
//
function processMath(i, j) {
var 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 (indent) block = block.replace(/\n /g, "\n");
// if (HUB.Browser.isMSIE) {
// block = block.replace(/(%[^\n]*)\n/g, "$1<br/>\n");
// }
while (j > i) blocks[j--] = "";
blocks[i] = "@@" + math.length + "@@";
math.push(block);
start = end = last = null;
}
let start = null;
let end = null;
let last = null;
let indent = null; // for tracking math delimiters
let braces = null;
const math = []; // stores math strings for latter
let blocks = capturingStringSplit(text.replace(/\r\n?/g, "\n"), SPLIT);
for (var i = 1, m = blocks.length; i < m; i += 2) {
var 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 or backticks,
// look for the end delimiter,
// but don't go past double line breaks,
// and balance braces within the math,
// but don't process math inside backticks.
//
if (block === end) {
if (braces > 0) {
last = i;
} else if (braces === 0) {
processMath(start, i);
} else {
start = end = last = null;
}
} else if (block.match(/\n.*\n/) || i + 2 >= m) {
if (last) {
i = last;
if (braces >= 0) processMath(start, i);
}
start = end = last = null;
braces = 0;
} else if (block === "{" && braces >= 0) {
braces++;
} else if (block === "}" && braces > 0) {
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;
} else if (block.charAt(0) === "`") {
start = last = i;
end = block;
braces = -1; // no brace balancing
} else if (block.charAt(0) === "\n") {
if (block.match(/ $/)) indent = true;
}
}
}
if (last) processMath(start, last);
// the commonmark renderer will render any `\$` as a simple `$`
// which could become a problem if `$` is used as a mathjax inline delimiter
// because then even escaped equations (starting with `\$`) would be detected
// as mathjax equations. Let's double-escape to make sure we still have a `\$`
// after commonmark did its conversion.
function doubleEscapeDelimiters(text, inline) {
if (!inline.startsWith("\\")) {
return text.replace(/\\\$/g, '\\\\$');
}
return text;
}
return { text: doubleEscapeDelimiters(blocks.join(""), inline), math };
}
//
// Put back the math strings that were saved,
// and clear the math array (no need to keep it around).
//
function replaceMath(input, math) {
const text = input.replace(/@@(\d+)@@/g, function(match, n) {
return math[n];
});
// math = null;
return text;
}
One platform to build and deploy the best data apps
Experiment and prototype by building visualizations in live JavaScript notebooks. Collaborate with your team and decide which concepts to build out.
Use Observable Framework to build data apps locally. Use data loaders to build in any language or library, including Python, SQL, and R.
Seamlessly deploy to Observable. Test before you ship, use automatic deploy-on-commit, and ensure your projects are always up-to-date.