Support \mathop, \mathrel, \mathbin, \mathpunct, etc. class commands.

These commands set their arguments in a given TeX math class. Use
the existing "op" type for \mathop (to support \limits); introduce
a new "mclass" type for the other classes.

Fixes #482. Tests borrowed from #485 (cbreeden).

src/buildHTML.js

@@ -786,6 +786,11 @@ groupTypes.op = function(group, options) {
 
         // The slant of the symbol is just its italic correction.
         slant = base.italic;
+    } else if (group.value.value) {
+        // If this is a list, compose that list.
+        var inner = buildExpression(group.value.value, options, true);
+
+        base = makeSpan(["mop"], inner, options);
     } else {
         // Otherwise, this is a text operator. Build the text from the
         // operator's name.
@@ -1399,6 +1404,12 @@ groupTypes.phantom = function(group, options) {
     return new buildCommon.makeFragment(elements);
 };
 
+groupTypes.mclass = function(group, options) {
+    var elements = buildExpression(group.value.value, options, true);
+
+    return makeSpan([group.value.mclass], elements, options);
+};
+
 /**
  * buildGroup is the function that takes a group and calls the correct groupType
  * function for it. It also handles the interaction of size and style changes

src/buildMathML.js

@@ -316,7 +316,7 @@ groupTypes.spacing = function(group) {
     return node;
 };
 
-groupTypes.op = function(group) {
+groupTypes.op = function(group, options) {
     var node;
 
     // TODO(emily): handle big operators using the `largeop` attribute
@@ -325,6 +325,10 @@ groupTypes.op = function(group) {
         // This is a symbol. Just add the symbol.
         node = new mathMLTree.MathNode(
             "mo", [makeText(group.value.body, group.mode)]);
+    } else if (group.value.value) {
+        // This is an operator with children. Add them.
+        node = new mathMLTree.MathNode(
+            "mo", buildExpression(group.value.value, options));
     } else {
         // This is a text operator. Add all of the characters from the
         // operator's name.
@@ -475,6 +479,11 @@ groupTypes.phantom = function(group, options) {
     return new mathMLTree.MathNode("mphantom", inner);
 };
 
+groupTypes.mclass = function(group, options) {
+    var inner = buildExpression(group.value.value, options);
+    return new mathMLTree.MathNode("mstyle", inner);
+};
+
 /**
  * Takes a list of nodes, builds them, and returns a list of the generated
  * MathML nodes. A little simpler than the HTML version because we don't do any

src/functions.js

@@ -100,6 +100,16 @@ function defineFunction(names, props, handler) {
     }
 }
 
+// Since the corresponding buildHTML/buildMathML function expects a
+// list of elements, we normalize for different kinds of arguments
+var ordargument = function(arg) {
+    if (arg.type === "ordgroup") {
+        return arg.value;
+    } else {
+        return [arg];
+    }
+};
+
 // A normal square root
 defineFunction("\\sqrt", {
     numArgs: 1,
@@ -121,19 +131,9 @@ defineFunction("\\text", {
     greediness: 2,
 }, function(context, args) {
     var body = args[0];
-    // Since the corresponding buildHTML/buildMathML function expects a
-    // list of elements, we normalize for different kinds of arguments
-    // TODO(emily): maybe this should be done somewhere else
-    var inner;
-    if (body.type === "ordgroup") {
-        inner = body.value;
-    } else {
-        inner = [body];
-    }
-
     return {
         type: "text",
-        body: inner,
+        body: ordargument(body),
     };
 });
 
@@ -146,18 +146,10 @@ defineFunction("\\color", {
 }, function(context, args) {
     var color = args[0];
     var body = args[1];
-    // Normalize the different kinds of bodies (see \text above)
-    var inner;
-    if (body.type === "ordgroup") {
-        inner = body.value;
-    } else {
-        inner = [body];
-    }
-
     return {
         type: "color",
         color: color.value,
-        value: inner,
+        value: ordargument(body),
     };
 });
 
@@ -223,16 +215,24 @@ defineFunction("\\phantom", {
     numArgs: 1,
 }, function(context, args) {
     var body = args[0];
-    var inner;
-    if (body.type === "ordgroup") {
-        inner = body.value;
-    } else {
-        inner = [body];
-    }
-
     return {
         type: "phantom",
-        value: inner,
+        value: ordargument(body),
+    };
+});
+
+// Math class commands except \mathop
+defineFunction([
+    "\\mathord", "\\mathbin", "\\mathrel", "\\mathopen",
+    "\\mathclose", "\\mathpunct", "\\mathinner",
+], {
+    numArgs: 1,
+}, function(context, args) {
+    var body = args[0];
+    return {
+        type: "mclass",
+        mclass: "m" + context.funcName.substr(5),
+        value: ordargument(body),
     };
 });
 
@@ -298,17 +298,10 @@ defineFunction([
     greediness: 3,
 }, function(context, args) {
     var body = args[0];
-    var atoms;
-    if (body.type === "ordgroup") {
-        atoms = body.value;
-    } else {
-        atoms = [body];
-    }
-
     return {
         type: "color",
         color: "katex-" + context.funcName.slice(1),
-        value: atoms,
+        value: ordargument(body),
     };
 });
 
@@ -378,6 +371,19 @@ defineFunction([
     };
 });
 
+// \mathop class command
+defineFunction("\\mathop", {
+    numArgs: 1,
+}, function(context, args) {
+    var body = args[0];
+    return {
+        type: "op",
+        limits: false,
+        symbol: false,
+        value: ordargument(body),
+    };
+});
+
 // Fractions
 defineFunction([
     "\\dfrac", "\\frac", "\\tfrac",

test/screenshotter/ss_data.yaml

@@ -79,6 +79,8 @@ LeftRightStyleSizing: |
 LimitControls: |
     \displaystyle\int\limits_2^3 3x^2\,dx + \sum\nolimits^n_{i=1}i +
     \textstyle\int\limits_x^y z
+MathAtom: a\mathrel{\mathop{=}\limits^{\blue ?}}b
+MathAtom2: \mathop{\overline\mathrm{lim}}\limits_{x\to\infty}f(x)
 MathDefaultFonts: Ax2k\breve{a}\omega\Omega\imath+\KaTeX
 MathBb: \mathbb{Ax2k\breve{a}\omega\Omega\imath+\KaTeX}
 MathBf: \mathbf{Ax2k\breve{a}\omega\Omega\imath+\KaTeX}