Implemented the "mix" builtin function.

context.cpp

@@ -36,6 +36,8 @@ namespace Sass {
     register_function(red_descriptor, red);
     register_function(green_descriptor, green);
     register_function(blue_descriptor, blue);
+    register_function(mix_2_descriptor, mix_2);
+    register_function(mix_3_descriptor, mix_3);
   }
   
 }
\ No newline at end of file

eval_apply.cpp

@@ -114,7 +114,12 @@ namespace Sass {
         }
       } break;
 
-      case Node::textual_percentage:
+      case Node::textual_percentage: {
+        Node pct(expr.line_number, std::atof(expr.content.token.begin));
+        pct.type = Node::numeric_percentage;
+        return pct;
+      } break;
+
       case Node::textual_dimension: {
         return Node(expr.line_number,
                     std::atof(expr.content.token.begin),

functions.cpp

@@ -10,10 +10,11 @@ namespace Sass {
     Function_Descriptor rgb_descriptor = 
     { "rgb", "$red", "$green", "$blue", 0 };
     Node rgb(const vector<Token>& parameters, map<Token, Node>& bindings) {
-      Node color(Node::numeric_color, 0, 3);
+      Node color(Node::numeric_color, 0, 4);
       color << bindings[parameters[0]]
             << bindings[parameters[1]]
-            << bindings[parameters[2]];
+            << bindings[parameters[2]]
+            << Node(0, 1.0);
       return color;
     }
 
@@ -31,7 +32,9 @@ namespace Sass {
     Function_Descriptor rgba_2_descriptor = 
     { "rgba", "$color", "$alpha", 0 };
     Node rgba_2(const vector<Token>& parameters, map<Token, Node>& bindings) {
-      return bindings[parameters[0]].clone() << bindings[parameters[1]];
+      Node color(bindings[parameters[0]].clone());
+      color[3] = bindings[parameters[1]];
+      return color;
     }
     
     Function_Descriptor red_descriptor =
@@ -52,5 +55,38 @@ namespace Sass {
       return bindings[parameters[0]][2];
     }
     
+    Node mix_impl(Node color1, Node color2, double weight) {
+      double p = weight/100;
+      double w = 2*p - 1;
+      double a = color1[3].content.numeric_value - color2[3].content.numeric_value;
+      
+      double w1 = (((w * a == -1) ? w : (w + a)/(1 + w*a)) + 1)/2.0;
+      double w2 = 1 - w1;
+      
+      Node mixed(Node::numeric_color, color1.line_number, 4);
+      for (int i = 0; i < 3; ++i) {
+        mixed << Node(mixed.line_number, w1*color1[i].content.numeric_value +
+                                         w2*color2[i].content.numeric_value);
+      }
+      double alpha = color1[3].content.numeric_value*p + color2[3].content.numeric_value*(1-p);
+      mixed << Node(mixed.line_number, alpha);
+      return mixed;
+    }
+    
+    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);
+    }
+    
+    Function_Descriptor mix_3_descriptor =
+    { "mix", "$color1", "$color2", "$weight", 0 };
+    Node mix_3(const vector<Token>& parameters, map<Token, Node>& bindings) {
+      return mix_impl(bindings[parameters[0]],
+                      bindings[parameters[1]],
+                      bindings[parameters[2]].content.numeric_value);
+    }
   }
 }
\ No newline at end of file

functions.hpp

@@ -60,6 +60,12 @@ namespace Sass {
     
     extern Function_Descriptor blue_descriptor;
     Node blue(const vector<Token>& parameters, map<Token, Node>& bindings);
+    
+    extern Function_Descriptor mix_2_descriptor;
+    Node mix_2(const vector<Token>& parameters, map<Token, Node>& bindings);
+    
+    extern Function_Descriptor mix_3_descriptor;
+    Node mix_3(const vector<Token>& parameters, map<Token, Node>& bindings);
   }
   
 }

node.cpp

@@ -141,6 +141,13 @@ namespace Sass {
         return "/";
       } break;
       
+      case numeric_percentage: {
+        stringstream ss;
+        ss << content.dimension.numeric_value;
+        ss << '%';
+        return ss.str();
+      }
+      
       case numeric_dimension: {
         stringstream ss;
         ss << content.dimension.numeric_value;
@@ -193,11 +200,11 @@ namespace Sass {
         }
         else {
           stringstream ss;
-          ss << "rgba(" << at(0).content.numeric_value;
-          for (int i = 1; i < 4; ++i) {
-            ss << ", " << at(i).content.numeric_value;
+          ss << "rgba(" << static_cast<unsigned long>(at(0).content.numeric_value);
+          for (int i = 1; i < 3; ++i) {
+            ss << ", " << static_cast<unsigned long>(at(i).content.numeric_value);
           }
-          ss << ')';
+          ss << ", " << at(3).content.numeric_value << ')';
           return ss.str();
         }
       } break;

spec/basic/22_colors_with_alpha/input.scss

@@ -16,4 +16,8 @@ div {
   hoo: red($x);
   moo: green($x);
   poo: blue($x);
+  
+  roo: mix(#f00, #00f);
+  doo: mix(#f00, #00f, 25%);
+  goo: mix(rgba(255, 0, 0, 0.5), #00f);
 }

spec/basic/22_colors_with_alpha/output.css

@@ -9,4 +9,7 @@ div {
   groo: aqua;
   hoo: 123;
   moo: 45;
-  poo: 6; }
+  poo: 6;
+  roo: #7f007f;
+  doo: #3f00bf;
+  goo: rgba(63, 0, 191, 0.75); }