type-checking stylesheet functions

is-string, is-keyword, is-color, is-number

lib/less/functions.js

@@ -174,6 +174,21 @@ tree.functions = {
         } else {
             throw { type: "Argument", message: "argument must be a string" };
         }
+    },
+    'is-color': function (n) {
+        return this._isa(n, tree.Color);
+    },
+    'is-number': function (n) {
+        return this._isa(n, tree.Dimension);
+    },
+    'is-string': function (n) {
+        return this._isa(n, tree.Quoted);
+    },
+    'is-keyword': function (n) {
+        return this._isa(n, tree.Keyword);
+    },
+    _isa: function (n, Type) {
+        return (n instanceof Type) ? tree.True : tree.False;
     }
 };
 

lib/less/tree/keyword.js

@@ -13,4 +13,7 @@ tree.Keyword.prototype = {
     }
 };
 
+tree.True = new(tree.Keyword)('true');
+tree.False = new(tree.Keyword)('false');
+
 })(require('../tree'));