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sagemathinc
GitHub Repository: sagemathinc/cocalc
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Path:
blob/master/src/packages/frontend/markdown/math-plugin.ts
Views: 179
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/*
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This is a revamp of https://github.com/goessner/markdown-it-texmath for our purposes.
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The original license with MIT, and we consider our modified version of it to also
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be MIT licensed.
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TODO: move this to a separate package hosted on npmjs.
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Original copyright:
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* Copyright (c) Stefan Goessner - 2017-21. All rights reserved.
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* Licensed under the MIT License. See License.txt in the project root for license information.
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CHANGES we made:
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- We don't care about using katex for rendering, so that code is gone.
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We only care about parsing.
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- RULES:
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The markdown-it-texmath plugin is very impressive, but it doesn't parse
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things like \begin{equation}x^3$\end{equation} without dollar signs.
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However, that is a basic requirement for cocalc in order to preserve
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Jupyter classic compatibility. So we define our own rules, inspired
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by the dollars rules from the the plugin,
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and extend the regexps to also recognize these. We do this with a new
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object "cocalc", to avoid potential conflicts.
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IMPORTANT: We remove the math_block_eqno from upstream, since it
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leads to very disturbing behavior and loss of information, e.g.,
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$$x$$
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(a) xyz
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Gets rendered with the xyz gone. Very confusing. Equation numbers
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when we do them, should be done as in latex, not with some weird notation that
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is surprising. See https://github.com/sagemathinc/cocalc/issues/5879
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*/
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const texmath = {
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inline: (rule) =>
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function inline(state, silent) {
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const pos = state.pos;
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const str = state.src;
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const pre =
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str.startsWith(rule.tag, (rule.rex.lastIndex = pos)) &&
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(!rule.pre || rule.pre(str, pos)); // valid pre-condition ...
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const match = pre && rule.rex.exec(str);
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const res =
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!!match &&
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pos < rule.rex.lastIndex &&
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(!rule.post || rule.post(str, rule.rex.lastIndex - 1));
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if (res) {
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if (!silent) {
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const token = state.push(rule.name, "math", 0);
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token.content = match[1];
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token.markup = rule.tag;
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}
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state.pos = rule.rex.lastIndex;
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}
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return res;
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},
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block: (rule) =>
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function block(state, begLine, endLine, silent) {
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const pos = state.bMarks[begLine] + state.tShift[begLine];
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const str = state.src;
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const pre =
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str.startsWith(rule.tag, (rule.rex.lastIndex = pos)) &&
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(!rule.pre || rule.pre(str, false, pos)); // valid pre-condition ....
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const match = pre && rule.rex.exec(str);
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const res =
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!!match &&
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pos < rule.rex.lastIndex &&
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(!rule.post || rule.post(str, false, rule.rex.lastIndex - 1));
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if (res && !silent) {
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// match and valid post-condition ...
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const endpos = rule.rex.lastIndex - 1;
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let curline;
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for (curline = begLine; curline < endLine; curline++)
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if (
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endpos >= state.bMarks[curline] + state.tShift[curline] &&
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endpos <= state.eMarks[curline]
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) {
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// line for end of block math found ...
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break;
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}
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// "this will prevent lazy continuations from ever going past our end marker"
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// https://github.com/markdown-it/markdown-it-container/blob/master/index.js
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const lineMax = state.lineMax;
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const parentType = state.parentType;
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state.lineMax = curline;
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state.parentType = "math";
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if (parentType === "blockquote") {
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// remove all leading '>' inside multiline formula
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match[1] = match[1].replace(/(\n*?^(?:\s*>)+)/gm, "");
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}
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// begin token
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let token = state.push(rule.name, "math", 0); // 'math_block'
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token.block = true;
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token.tag = rule.tag;
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token.markup = "";
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token.content = match[1];
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token.map = [begLine, curline + 1]; // WARNING: this +1 is also fixes an upstream bug. Getting this right is critical for caching in slate.
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// end token ... superfluous ...
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state.parentType = parentType;
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state.lineMax = lineMax;
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state.line = curline + 1;
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}
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return res;
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},
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render: (tex, displayMode) => {
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// We need to continue to support rendering to MathJax as an option,
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// but texmath only supports katex. Thus we output by default to
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// html using script tags, which are then parsed later using our
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// katex/mathjax plugin.
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return `<script type="math/tex${
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displayMode ? "; mode=display" : ""
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}">${tex}</script>`;
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},
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// used for enable/disable math rendering by `markdown-it`
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inlineRuleNames: ["math_inline", "math_inline_double"],
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blockRuleNames: ["math_block"],
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rules: {
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cocalc: {
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inline: [
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{
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name: "math_inline_double",
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rex: /\${2}([^$]*?[^\\])\${2}/gy,
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tag: "$$",
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displayMode: true,
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pre,
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post,
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},
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{
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// We modify this from what's included in markdown-it-texmath to allow for
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// multiple line inline formulas, e.g., "$2+\n3$" should work, but doesn't in upstream.
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name: "math_inline",
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rex: /\$((?:[^\$\s\\])|(?:[\S\s]*?[^\\]))\$/gmy,
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tag: "$",
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outerSpace: false,
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pre,
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post,
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},
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{
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// using \begin/\end as part of inline markdown...
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name: "math_inline",
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rex: /(\\(?:begin)(\{math\})[\s\S]*?\\(?:end)\2)/gmy,
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tag: "\\",
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displayMode: false,
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pre,
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post,
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},
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{
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// using \begin/\end as part of inline markdown...
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name: "math_inline_double",
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rex: /(\\(?:begin)(\{[a-z]*\*?\})[\s\S]*?\\(?:end)\2)/gmy,
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tag: "\\",
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displayMode: true,
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pre,
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post,
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},
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],
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block: [
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{
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name: "math_block",
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rex: /\${2}([^$]*?[^\\])\${2}/gmy,
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tag: "$$",
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},
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{
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name: "math_block",
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rex: /(\\(?:begin)(\{[a-z]*\*?\})[\s\S]*?\\(?:end)\2)/gmy, // regexp to match \begin{...}...\end{...} environment.
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tag: "\\",
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},
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],
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},
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},
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};
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export default function mathPlugin(md) {
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for (const rule of texmath.rules["cocalc"].inline) {
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md.inline.ruler.before("escape", rule.name, texmath.inline(rule)); // ! important
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md.renderer.rules[rule.name] = (tokens, idx) =>
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texmath.render(tokens[idx].content, !!rule.displayMode);
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}
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for (const rule of texmath.rules["cocalc"].block) {
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md.block.ruler.before("fence", rule.name, texmath.block(rule)); // ! important for ```math delimiters
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md.renderer.rules[rule.name] = (tokens, idx) =>
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texmath.render(tokens[idx].content, true);
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}
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}
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function pre(str, beg) {
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const prv = beg > 0 ? str[beg - 1].charCodeAt(0) : false;
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return (
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!prv ||
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(prv !== 0x5c && // no backslash,
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(prv < 0x30 || prv > 0x39))
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); // no decimal digit .. before opening '$'
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}
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function post(str, end) {
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const nxt = str[end + 1] && str[end + 1].charCodeAt(0);
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return !nxt || nxt < 0x30 || nxt > 0x39; // no decimal digit .. after closing '$'
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}
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