Implement correct macros for liminf and limsup, fixes #111 (#887)

* Implement correct macros for liminf and limsup, fixes #111

* fix nits

src/buildMathML.js

@@ -198,9 +198,19 @@ groupTypes.supsub = function(group, options) {
     if (isBrace) {
         nodeType = (isOver ? "mover" : "munder");
     } else if (!group.value.sub) {
-        nodeType = "msup";
+        const base = group.value.base;
+        if (base && base.value.limits && options.style === Style.DISPLAY) {
+            nodeType = "mover";
+        } else {
+            nodeType = "msup";
+        }
     } else if (!group.value.sup) {
-        nodeType = "msub";
+        const base = group.value.base;
+        if (base && base.value.limits && options.style === Style.DISPLAY) {
+            nodeType = "munder";
+        } else {
+            nodeType = "msub";
+        }
     } else {
         const base = group.value.base;
         if (base && base.value.limits && options.style === Style.DISPLAY) {

src/functions.js

@@ -181,8 +181,7 @@ defineFunction([
 
 // Limits, not symbols
 defineFunction([
-    "\\det", "\\gcd", "\\inf", "\\lim", "\\liminf", "\\limsup", "\\max",
-    "\\min", "\\Pr", "\\sup",
+    "\\det", "\\gcd", "\\inf", "\\lim", "\\max", "\\min", "\\Pr", "\\sup",
 ], {
     numArgs: 0,
 }, function(context) {

src/functions/operatorname.js

@@ -30,22 +30,27 @@ defineFunction({
             let mode = "";
 
             // Consolidate Greek letter function names into symbol characters.
-            const temp = html.buildExpression(group.value.value, options, true);
+            const temp = html.buildExpression(
+                group.value.value, options.withFontFamily("mathrm"), true);
 
             // All we want from temp are the letters. With them, we'll
             // create a text operator similar to \tan or \cos.
-            for (let i = 0; i < temp.length; i++) {
-                letter = temp[i].value;
+            for (const child of temp) {
+                if (child instanceof domTree.symbolNode) {
+                    letter = child.value;
 
-                // In the amsopn package, \newmcodes@ changes four
-                // characters, *-/:’, from math operators back into text.
-                // Given what is in temp, we have to address two of them.
-                letter = letter.replace(/\u2212/, "-");   // minus => hyphen
-                letter = letter.replace(/\u2217/, "*");
+                    // In the amsopn package, \newmcodes@ changes four
+                    // characters, *-/:’, from math operators back into text.
+                    // Given what is in temp, we have to address two of them.
+                    letter = letter.replace(/\u2212/, "-");   // minus => hyphen
+                    letter = letter.replace(/\u2217/, "*");
 
-                // Use math mode for Greek letters
-                mode = (/[\u0391-\u03D7]/.test(letter) ? "math" : "text");
-                output.push(buildCommon.mathsym(letter, mode));
+                    // Use math mode for Greek letters
+                    mode = (/[\u0391-\u03D7]/.test(letter) ? "math" : "text");
+                    output.push(buildCommon.mathsym(letter, mode));
+                } else {
+                    output.push(child);
+                }
             }
         }
         return buildCommon.makeSpan(["mop"], output, options);
@@ -55,12 +60,11 @@ defineFunction({
         // The steps taken here are similar to the html version.
         let output = [];
         if (group.value.value.length > 0) {
-            const temp = mml.buildExpression(group.value.value, options);
+            const temp = mml.buildExpression(
+                group.value.value, options.withFontFamily("mathrm"));
+
+            let word = temp.map(node => node.toText()).join("");
 
-            let word = "";
-            for (let i = 0; i < temp.length; i++) {
-                word += temp[i].children[0].text;
-            }
             word = word.replace(/\u2212/g, "-");
             word = word.replace(/\u2217/g, "*");
             output = [new mathMLTree.TextNode(word)];

src/macros.js

@@ -399,3 +399,5 @@ defineMacro("\\approxcoloncolon",
 //       macro turned into a propper defineSymbol in symbols.js. That way, the
 //       MathML result will be much cleaner.
 defineMacro("\\notni", "\\not\\ni");
+defineMacro("\\limsup", "\\DOTSB\\mathop{\\operatorname{lim\\,sup}}\\limits");
+defineMacro("\\liminf", "\\DOTSB\\mathop{\\operatorname{lim\\,inf}}\\limits");

src/mathMLTree.js

@@ -93,6 +93,22 @@ class MathNode {
 
         return markup;
     }
+
+    /**
+     * Converts the math node into a string, similar to innerText.
+     */
+    toText(): string {
+        if (this.type === "mspace") {
+            if (this.attributes.width === "0.16667em") {
+                return "\u2006";
+            } else {
+                // TODO: Use other space characters for different widths.
+                // https://github.com/Khan/KaTeX/issues/1036
+                return " ";
+            }
+        }
+        return this.children.map(child => child.toText()).join("");
+    }
 }
 
 /**
@@ -118,6 +134,13 @@ class TextNode {
     toMarkup(): string {
         return utils.escape(this.text);
     }
+
+    /**
+     * Converts the text node into a string (which is just the text iteself).
+     */
+    toText(): string {
+        return this.text;
+    }
 }
 
 export default {