From 5ec708c3f4674e6e3cfec28bb4f733a8a0e69b9a Mon Sep 17 00:00:00 2001
From: Alexis Sellier <alexis@cloudhead.io>
Date: Tue, 3 Jan 2012 18:45:31 +0100
Subject: [PATCH] type-checking stylesheet functions

is-string, is-keyword, is-color, is-number
---
 lib/less/functions.js    | 15 +++++++++++++++
 lib/less/tree/keyword.js |  3 +++
 test/css/functions.css   |  8 ++++++++
 test/less/functions.less |  9 +++++++++
 4 files changed, 35 insertions(+)

diff --git a/lib/less/functions.js b/lib/less/functions.js
index 4a2a6fb9..f93a5c4b 100644
--- a/lib/less/functions.js
+++ b/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;
     }
 };
 
diff --git a/lib/less/tree/keyword.js b/lib/less/tree/keyword.js
index 2a703fc6..701b79e5 100644
--- a/lib/less/tree/keyword.js
+++ b/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'));
diff --git a/test/css/functions.css b/test/css/functions.css
index 4eee191f..f823a992 100644
--- a/test/css/functions.css
+++ b/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);
 }
diff --git a/test/less/functions.less b/test/less/functions.less
index 2045a85d..44f4242c 100644
--- a/test/less/functions.less
+++ b/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 {