Implemented the "invert" builtin.

context.cpp

@@ -30,6 +30,7 @@ namespace Sass {
   void Context::register_functions()
   {
     using namespace Functions;
+    // RGB Functions
     register_function(rgb_descriptor,  rgb);
     register_function(rgba_4_descriptor, rgba_4);
     register_function(rgba_2_descriptor, rgba_2);
@@ -38,6 +39,8 @@ namespace Sass {
     register_function(blue_descriptor, blue);
     register_function(mix_2_descriptor, mix_2);
     register_function(mix_3_descriptor, mix_3);
+    // HSL Functions
+    register_function(invert_descriptor, invert);
   }
   
 }
\ No newline at end of file

functions.cpp

@@ -7,6 +7,8 @@ namespace Sass {
 
     // TO DO: functions need to check the types of their arguments
 
+    // RGB Functions ///////////////////////////////////////////////////////
+
     Function_Descriptor rgb_descriptor = 
     { "rgb", "$red", "$green", "$blue", 0 };
     Node rgb(const vector<Token>& parameters, map<Token, Node>& bindings) {
@@ -55,7 +57,7 @@ namespace Sass {
       return bindings[parameters[0]][2];
     }
     
-    Node mix_impl(Node color1, Node color2, double weight) {
+    Node mix_impl(Node color1, Node color2, double weight = 50) {
       double p = weight/100;
       double w = 2*p - 1;
       double a = color1[3].content.numeric_value - color2[3].content.numeric_value;
@@ -76,9 +78,7 @@ namespace Sass {
     Function_Descriptor mix_2_descriptor =
     { "mix", "$color1", "$color2", 0 };
     Node mix_2(const vector<Token>& parameters, map<Token, Node>& bindings) {
-      return mix_impl(bindings[parameters[0]],
-                      bindings[parameters[1]],
-                      50);
+      return mix_impl(bindings[parameters[0]], bindings[parameters[1]]);
     }
     
     Function_Descriptor mix_3_descriptor =
@@ -88,5 +88,57 @@ namespace Sass {
                       bindings[parameters[1]],
                       bindings[parameters[2]].content.numeric_value);
     }
+    
+    // HSL Functions ///////////////////////////////////////////////////////
+    
+    Function_Descriptor invert_descriptor =
+    { "invert", "$color", 0 };
+    Node invert(const vector<Token>& parameters, map<Token, Node>& bindings) {
+      Node orig(bindings[parameters[0]]);
+      return Node(orig.line_number,
+                  255 - orig[0].content.numeric_value,
+                  255 - orig[1].content.numeric_value,
+                  255 - orig[2].content.numeric_value,
+                  orig[3].content.numeric_value);
+    }
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   }
 }
\ No newline at end of file

functions.hpp

@@ -66,6 +66,9 @@ namespace Sass {
     
     extern Function_Descriptor mix_3_descriptor;
     Node mix_3(const vector<Token>& parameters, map<Token, Node>& bindings);
+    
+    extern Function_Descriptor invert_descriptor;
+    Node invert(const vector<Token>& parameters, map<Token, Node>& bindings);
   }
   
 }

spec/basic/22_colors_with_alpha/input.scss

@@ -20,4 +20,6 @@ div {
   roo: mix(#f00, #00f);
   doo: mix(#f00, #00f, 25%);
   goo: mix(rgba(255, 0, 0, 0.5), #00f);
+  
+  boo: invert(#123456);
 }

spec/basic/22_colors_with_alpha/output.css

@@ -12,4 +12,5 @@ div {
   poo: 6;
   roo: #7f007f;
   doo: #3f00bf;
-  goo: rgba(63, 0, 191, 0.75); }
+  goo: rgba(63, 0, 191, 0.75);
+  boo: #edcba9; }