Add comments (for Volker).

Author: dpvc

unpacked/jax/input/TeX/jax.js

@@ -1685,12 +1685,33 @@
     Entry: function (name) {
       this.Push(STACKITEM.cell().With({isEntry: true, name: name}));
       if (this.stack.Top().isCases) {
+        //
+        //  Make second column be in \text{...} (unless it is already
+        //  in a \text{...}, for backward compatibility).
+        //
         var string = this.string;
         var braces = 0, close = -1, i = this.i, m = string.length;
+        //
+        //  Look through the string character by character...
+        //
         while (i < m) {
           var c = string.charAt(i);
-          if (c === "{") {braces++; i++}
-          else if (c === "}") {
+          if (c === "{") {
+            //
+            //  Increase the nested brace count and go on
+            //
+            braces++;
+            i++;
+          } else if (c === "}") {
+            //
+            //  If there are too many close braces, just end (we will get an
+            //    error message later when the rest of the string is parsed)
+            //  Otherwise
+            //    decrease the nested brace count,
+            //    if it is now zero and we haven't already marked the end of the
+            //      first brace group, record the position (use to check for \text{} later)
+            //    go on to the next character.
+            //
             if (braces === 0) {
               m = 0;
             } else {
@@ -1701,11 +1722,29 @@
               i++;
             }
           } else if (c === "&" && braces === 0) {
+            //
+            //  Extra alignment tabs are not allowed in cases
+            //
             TEX.Error(["ExtraAlignTab","Extra alignment tab in \\cases text"]);
           } else if (c === "\\") {
+            //
+            //  If the macro is \cr or \\, end the search, otherwise skip the macro
+            //  (multi-letter names don't matter, as we will skip the rest of the
+            //   characters in the main loop)
+            //
             if (string.substr(i).match(/^((\\cr)[^a-zA-Z]|\\\\)/)) {m = 0} else {i += 2}
-          } else {i++}
+          } else {
+            //
+            //  Go on to the next character
+            //
+            i++;
+          }
         }
+        //
+        //  Check if the second column text is already in \text{},
+        //  If not, process the second column as text and continue parsing from there,
+        //    (otherwise process the second column as normal, since it is in \text{}
+        //
         var text = string.substr(this.i,i-this.i);
         if (!text.match(/^\s*\\text[^a-zA-Z]/) || close !== text.replace(/\s+$/,'').length - 1) {
           this.Push.apply(this,this.InternalMath(text,0));