Metaprogramming cleanup.

lib/lang/english.js

@@ -1,13 +1,14 @@
-function shared_prefix_length(a, b) {
-  var i = 0;
-  while(i !== a.length && i !== b.length && a.charCodeAt(i) === b.charCodeAt(i))
-    ++i;
-  return i;
-}
+function join_with_shared_prefix(joiner) {
+  return function(a, b) {
+    var i = 0;
+
+    while(i !== a.length &&
+          i !== b.length &&
+          a.charCodeAt(i) === b.charCodeAt(i))
+      ++i;
 
-function join_with_shared_prefix(a, b, joiner) {
-  var length = shared_prefix_length(a, b);
-  return a.slice(0, length) + a.slice(length) + joiner + b.slice(length);
+    return a.slice(0, i) + a.slice(i) + joiner + b.slice(i);
+  };
 }
 
 module.exports = require("../template")({
@@ -69,12 +70,8 @@ module.exports = require("../template")({
   "minutes": "$1 min.",
   "fahrenheit": "$1\u00B0F",
   "celsius": "$1\u00B0C",
-  "and": function(a, b) {
-    return join_with_shared_prefix(a, b, " and ");
-  },
-  "range": function(a, b) {
-    return join_with_shared_prefix(a, b, " through ");
-  },
+  "and": join_with_shared_prefix(" and "),
+  "range": join_with_shared_prefix(" through "),
   "then": "$1, then $2",
   "clauses": function(one, two) {
     return one +