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'));

test/css/functions.css

@@ -27,6 +27,14 @@
   percentage: 20%;
   color: #ff0011;
 }
+#built-in .is-a {
+  color: true;
+  color: true;
+  color: true;
+  keyword: true;
+  number: true;
+  string: true;
+}
 #alpha {
   alpha: rgba(153, 94, 51, 0.6);
 }

test/less/functions.less

@@ -30,6 +30,15 @@
   roundedpx: round(10px / 3);
   percentage: percentage(10px / 50);
   color: color("#ff0011");
+
+  .is-a {
+    color: is-color(#ddd);
+    color: is-color(red);
+    color: is-color(rgb(0, 0, 0));
+    keyword: is-keyword(hello);
+    number: is-number(32);
+    string: is-string("hello");
+  }
 }
 
 #alpha {