Implementing the 'if' built-in function.

context.cpp

@@ -158,6 +158,7 @@ namespace Sass {
     register_function(comparable_descriptor, comparable);
     // Boolean Functions
     register_function(not_descriptor, not_impl);
+    register_function(if_descriptor, if_impl);
   }
 
   void Context::setup_color_map()

functions.cpp

@@ -748,7 +748,7 @@ namespace Sass {
     
     // Boolean Functions ///////////////////////////////////////////////////
     Function_Descriptor not_descriptor =
-    { "not", "value", 0 };
+    { "not", "$value", 0 };
     Node not_impl(const Node parameters, map<Token, Node>& bindings, Node_Factory& new_Node) {
       Node val(bindings[parameters[0].token()]);
       if (val.type() == Node::boolean && val.boolean_value() == false) {
@@ -759,5 +759,16 @@ namespace Sass {
       }
     }
 
+    Function_Descriptor if_descriptor =
+    { "if", "$predicate", "$consequent", "$alternative", 0 };
+    Node if_impl(const Node parameters, map<Token, Node>& bindings, Node_Factory& new_Node) {
+      Node predicate(bindings[parameters[0].token()]);
+      Node consequent(bindings[parameters[1].token()]);
+      Node alternative(bindings[parameters[2].token()]);
+
+      if (predicate.type() == Node::boolean && predicate.boolean_value() == false) return alternative;
+      return consequent;
+    }
+
   }
 }

functions.hpp

@@ -196,6 +196,9 @@ namespace Sass {
     extern Function_Descriptor not_descriptor;
     Node not_impl(const Node parameters, map<Token, Node>& bindings, Node_Factory& new_Node);
 
+    extern Function_Descriptor if_descriptor;
+    Node if_impl(const Node parameters, map<Token, Node>& bindings, Node_Factory& new_Node);
+
   }
   
 }