Support {rcases} and {drcases} (#2149)

* Support {rcases} and {drcases}

* Fix lint error

* Update screenshots

docs/support_table.md

@@ -338,6 +338,7 @@ use `\ce` instead|
 |\downdownarrows|$\downdownarrows$||
 |\downharpoonleft|$\downharpoonleft$||
 |\downharpoonright|$\downharpoonright$||
+|{drcases}|$\begin{drcases}a&\text{if }b\\c&\text{if }d\end{drcases}$|`\begin{drcases}`<br>&nbsp;&nbsp;&nbsp;`a &\text{if } b  \\`<br>&nbsp;&nbsp;&nbsp;`c &\text{if } d`<br>`\end{drcases}`|
 
 ## E
 
@@ -847,6 +848,7 @@ use `\ce` instead|
 |\rBrace|$\rBrace$||
 |\rbrace|$\rbrace$||
 |\rbrack|$\rbrack$||
+|{rcases}|$\begin{rcases}a&\text{if }b\\c&\text{if }d\end{rcases}$|`\begin{rcases}`<br>&nbsp;&nbsp;&nbsp;`a &\text{if } b  \\`<br>&nbsp;&nbsp;&nbsp;`c &\text{if } d`<br>`\end{rcases}`|
 |\rceil|$\rceil$||
 |\Re|$\Re$||
 |\real|$\real$||

docs/supported.md

@@ -85,11 +85,11 @@ $( \big( \Big( \bigg( \Bigg($ `( \big( \Big( \bigg( \Bigg(`
 |$\begin{Bmatrix} a & b \\ c & d \end{Bmatrix}$ |`\begin{Bmatrix}`<br>&nbsp;&nbsp;&nbsp;`a & b \\`<br>&nbsp;&nbsp;&nbsp;`c & d`<br>`\end{Bmatrix}`|$\def\arraystretch{1.5}\begin{array}{c:c:c} a & b & c \\ \hline d & e & f \\ \hdashline g & h & i \end{array}$|`\def\arraystretch{1.5}`<br>&nbsp;&nbsp;&nbsp;`\begin{array}{c:c:c}`<br>&nbsp;&nbsp;&nbsp;`a & b & c \\ \hline`<br>&nbsp;&nbsp;&nbsp;`d & e & f \\`<br>&nbsp;&nbsp;&nbsp;`\hdashline`<br>&nbsp;&nbsp;&nbsp;`g & h & i`<br>`\end{array}`
 |$\begin{aligned} a&=b+c \\ d+e&=f \end{aligned}$ |`\begin{aligned}`<br>&nbsp;&nbsp;&nbsp;`a&=b+c \\`<br>&nbsp;&nbsp;&nbsp;`d+e&=f`<br>`\end{aligned}`|$\begin{alignedat}{2}10&x+&3&y=2\\3&x+&13&y=4\end{alignedat}$ |`\begin{alignedat}{2}`<br>&nbsp;&nbsp;&nbsp;`10&x+ &3&y = 2 \\`<br>&nbsp;&nbsp;&nbsp;` 3&x+&13&y = 4`<br>`\end{alignedat}`
 |$\begin{gathered} a=b \\ e=b+c \end{gathered}$ |`\begin{gathered}`<br>&nbsp;&nbsp;&nbsp;`a=b \\ `<br>&nbsp;&nbsp;&nbsp;`e=b+c`<br>`\end{gathered}`|$x = \begin{cases} a &\text{if } b \\ c &\text{if } d \end{cases}$ |`x = \begin{cases}`<br>&nbsp;&nbsp;&nbsp;`a &\text{if } b  \\`<br>&nbsp;&nbsp;&nbsp;`c &\text{if } d`<br>`\end{cases}`
-|$\begin{smallmatrix} a & b \\ c & d \end{smallmatrix}$ | `\begin{smallmatrix}`<br>&nbsp;&nbsp;&nbsp;`a & b \\`<br>&nbsp;&nbsp;&nbsp;`c & d`<br>`\end{smallmatrix}` | | |
+|$\begin{smallmatrix} a & b \\ c & d \end{smallmatrix}$ | `\begin{smallmatrix}`<br>&nbsp;&nbsp;&nbsp;`a & b \\`<br>&nbsp;&nbsp;&nbsp;`c & d`<br>`\end{smallmatrix}` |$\begin{rcases} a &\text{if } b \\ c &\text{if } d \end{rcases}⇒…$ |`\begin{rcases}`<br>&nbsp;&nbsp;&nbsp;`a &\text{if } b  \\`<br>&nbsp;&nbsp;&nbsp;`c &\text{if } d`<br>`\end{rcases}⇒…`|
 
 </div>
 
-KaTeX also supports `darray`  and `dcases`.
+KaTeX also supports `darray`, `dcases`, and `drcases`.
 
 Acceptable line separators include: `\\`, `\cr`, `\\[distance]`, and `\cr[distance]`. *Distance* can be written with any of the [KaTeX units](#units).
 

src/environments/array.js

@@ -752,11 +752,14 @@ defineEnvironment({
 // \left\{\begin{array}{@{}l@{\quad}l@{}} … \end{array}\right.
 // {dcases} is a {cases} environment where cells are set in \displaystyle,
 // as defined in mathtools.sty.
+// {rcases} is another mathtools environment. It's brace is on the right side.
 defineEnvironment({
     type: "array",
     names: [
         "cases",
         "dcases",
+        "rcases",
+        "drcases",
     ],
     props: {
         numArgs: 0,
@@ -786,8 +789,8 @@ defineEnvironment({
             type: "leftright",
             mode: context.mode,
             body: [res],
-            left: "\\{",
-            right: ".",
+            left: context.envName.indexOf("r") > -1 ? "." : "\\{",
+            right: context.envName.indexOf("r") > -1 ? "\\}" : ".",
             rightColor: undefined,
         };
     },

test/katex-spec.js

@@ -2646,6 +2646,15 @@ describe("A cases environment", function() {
 
 });
 
+describe("An rcases environment", function() {
+
+    it("should build", function() {
+        expect`\begin{rcases} a &\text{if } b \\ c &\text{if } d \end{rcases}⇒…`
+            .toBuild();
+    });
+
+});
+
 describe("An aligned environment", function() {
 
     it("should parse its input", function() {

test/screenshotter/ss_data.yaml

@@ -74,7 +74,11 @@ Cases: |
         a+1&\text{if }b\text{ is odd} \\
         a&\text{if }b=0 \\
         a-1&\text{otherwise}
-    \end{cases}
+    \end{cases} \\
+    \begin{rcases}
+        a &\text{if } b \\
+        c &\text{if } d
+    \end{rcases}⇒…
 Colors:
     tex: \blue{a}\textcolor{#0f0}{b}\textcolor{red}{c}
     nolatex: different syntax and different scope