David Kutugata (DavidKutu) · Oct 28, 2019 · Oct 24, 2019 · Oct 25, 2019 · Oct 25, 2019 · Oct 28, 2019
diff --git a/news/2 Fixes/7992.md b/news/2 Fixes/7992.md
@@ -0,0 +1 @@
+Can now include a LaTeX-style equation without surrounding the equation with '$' in a markdown cell.
diff --git a/src/datascience-ui/interactive-common/cellOutput.tsx b/src/datascience-ui/interactive-common/cellOutput.tsx
@@ -1,19 +1,12 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 'use strict';
-import '../../client/common/extensions';
-
-// tslint:disable-next-line: no-var-requires no-require-imports
-const ansiToHtml = require('ansi-to-html');
-
 import { nbformat } from '@jupyterlab/coreutils';
 import { JSONObject } from '@phosphor/coreutils';
 import ansiRegex from 'ansi-regex';
-// tslint:disable-next-line: no-require-imports
-import cloneDeep = require('lodash/cloneDeep');
 import * as monacoEditor from 'monaco-editor/esm/vs/editor/editor.api';
 import * as React from 'react';
-
+import '../../client/common/extensions';
 import { concatMultilineStringInput, concatMultilineStringOutput } from '../../client/datascience/common';
 import { Identifiers } from '../../client/datascience/constants';
 import { CellState } from '../../client/datascience/types';
@@ -22,9 +15,16 @@ import { noop } from '../../test/core';
 import { Image, ImageName } from '../react-common/image';
 import { ImageButton } from '../react-common/imageButton';
 import { getLocString } from '../react-common/locReactSide';
+import { fixLatexEquations } from './latexManipulation';
 import { ICellViewModel } from './mainState';
 import { displayOrder, richestMimetype, transforms } from './transforms';
 
+// tslint:disable-next-line: no-var-requires no-require-imports
+const ansiToHtml = require('ansi-to-html');
+
+// tslint:disable-next-line: no-require-imports
+import cloneDeep = require('lodash/cloneDeep');
+
 interface ICellOutputProps {
     cellVM: ICellViewModel;
     baseTheme: string;
@@ -172,7 +172,7 @@ export class CellOutput extends React.Component<ICellOutputProps> {
     private renderMarkdownOutputs = () => {
         const markdown = this.getMarkdownCell();
         // React-markdown expects that the source is a string
-        const source = concatMultilineStringInput(markdown.source);
+        const source = fixLatexEquations(concatMultilineStringInput(markdown.source));
         const Transform = transforms['text/markdown'];
         const MarkdownClassName = 'markdown-cell-output';
 

diff --git a/src/datascience-ui/interactive-common/latexManipulation.ts b/src/datascience-ui/interactive-common/latexManipulation.ts
@@ -0,0 +1,38 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+// Adds '$$' to latex formulas that don't have a '$', allowing users to input the formula directly.
+export function fixLatexEquations(input: string): string {
+    const block = '\n$$\n';
+
+    const beginIndexes = getAllIndexesOfRegex(input, /\\begin\{[a-z]*\*?\}/g);
+    const endIndexes = getAllIndexesOfRegex(input, /\\end\{[a-z]*\*?\}/g);
+
+    if (beginIndexes.length === endIndexes.length) {
+        for (let i = 0; i < beginIndexes.length; i += 1) {
+            const endOfEnd = input.indexOf('}', endIndexes[i] + 1 + 8 * i);
+
+            // Edge case, if the input starts with the latex formula we add the block at the beggining.
+            if (beginIndexes[i] === 0 && input[beginIndexes[i]] === '\\') {
+                input = block + input.slice(0, endOfEnd + 1) + block + input.slice(endOfEnd + 1, input.length);
+                // Normal case, if the latex formula starts with a '$' we don't do anything.
+                // Otherwise, we insert the block at the beginning and ending of the latex formula.
+            } else if (input[beginIndexes[i] - 1] !== '$') {
+                input = input.slice(0, beginIndexes[i] + block.length * 2 * i) + block + input.slice(beginIndexes[i] + block.length * 2 * i, endOfEnd + 1) + block + input.slice(endOfEnd + 1, input.length);
+            }
+        }
+    }
+
+    return input;
+}
+
+function getAllIndexesOfRegex(arr: string, value: RegExp): number[] {
+    const indexes = [];
+    let result;
+
+    // tslint:disable-next-line: no-conditional-assignment
+    while ((result = value.exec(arr)) !== null) {
+        indexes.push(result.index);
+    }
+
+    return indexes;
+}
diff --git a/src/test/datascience/latexManipulation.unit.test.ts b/src/test/datascience/latexManipulation.unit.test.ts
@@ -0,0 +1,102 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+'use strict';
+import { expect } from 'chai';
+import { fixLatexEquations } from '../../datascience-ui/interactive-common/latexManipulation';
+
+// tslint:disable: max-func-body-length
+suite('Data Science - LaTeX Manipulation', () => {
+    const markdown1 = `\\begin{align}
+\\nabla \\cdot \\vec{\\mathbf{E}} & = 4 \\pi \\rho \\\\
+\\nabla \\times \\vec{\\mathbf{E}}\\, +\\, \\frac1c\\, \\frac{\\partial\\vec{\\mathbf{B}}}{\\partial t} & = \\vec{\\mathbf{0}} \\\\
+\\nabla \\cdot \\vec{\\mathbf{B}} & = 0
+\\end{align}
+sample text`;
+
+    const output1 = `
+$$
+\\begin{align}
+\\nabla \\cdot \\vec{\\mathbf{E}} & = 4 \\pi \\rho \\\\
+\\nabla \\times \\vec{\\mathbf{E}}\\, +\\, \\frac1c\\, \\frac{\\partial\\vec{\\mathbf{B}}}{\\partial t} & = \\vec{\\mathbf{0}} \\\\
+\\nabla \\cdot \\vec{\\mathbf{B}} & = 0
+\\end{align}
+$$
+
+sample text`;
+
+    const markdown2 = `$\\begin{align*}
+(a+b)^2 = a^2+2ab+b^2
+\\end{align*}$
+sample text
+$\\begin{align*}
+(a+b)^2 = a^2+2ab+b^2
+\\end{align*}$
+sample text`;
+
+    const markdown3 = `\\begin{align*}
+(a+b)^2 = a^2+2ab+b^2
+\\end{align*}
+sample text
+\\begin{align*}
+(a+b)^2 = a^2+2ab+b^2
+\\end{align*}
+sample text
+\\begin{align*}
+(a+b)^2 = a^2+2ab+b^2
+\\end{align*}
+sample text
+
+sample text
+\\begin{align*}
+(a+b)^2 = a^2+2ab+b^2
+\\end{align*}`;
+
+    const output3 = `
+$$
+\\begin{align*}
+(a+b)^2 = a^2+2ab+b^2
+\\end{align*}
+$$
+
+sample text
+
+$$
+\\begin{align*}
+(a+b)^2 = a^2+2ab+b^2
+\\end{align*}
+$$
+
+sample text
+
+$$
+\\begin{align*}
+(a+b)^2 = a^2+2ab+b^2
+\\end{align*}
+$$
+
+sample text
+
+sample text
+
+$$
+\\begin{align*}
+(a+b)^2 = a^2+2ab+b^2
+\\end{align*}
+$$
+`;
+
+    test('Latex - Equations don\'t have $$', () => {
+        const result = fixLatexEquations(markdown1);
+        expect(result).to.be.equal(output1, 'Result is incorrect');
+    });
+
+    test('Latex - Equations have $', () => {
+        const result = fixLatexEquations(markdown2);
+        expect(result).to.be.equal(markdown2, 'Result is incorrect');
+    });
+
+    test('Latex - Multiple equations don\'t have $$', () => {
+        const result = fixLatexEquations(markdown3);
+        expect(result).to.be.equal(output3, 'Result is incorrect');
+    });
+});
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Can now include a LaTeX-style equation without surrounding the equation with '$' in a markdown cell.