Implemented "opacify" and "transparentize" and their aliases.

context.cpp

@@ -44,6 +44,10 @@ namespace Sass {
     // Opacity Functions
     register_function(alpha_descriptor, alpha);
     register_function(opacity_descriptor, alpha);
+    register_function(opacify_descriptor, opacify);
+    register_function(fade_in_descriptor, opacify);
+    register_function(transparentize_descriptor, transparentize);
+    register_function(fade_out_descriptor, transparentize);
     // String Functions
     register_function(unquote_descriptor, unquote);
     register_function(quote_descriptor, quote);

functions.cpp

 #include "functions.hpp"
 #include <iostream>
+#include <cmath>
 using std::cerr; using std::endl;
 
 namespace Sass {
@@ -111,6 +112,28 @@ namespace Sass {
     Node alpha(const vector<Token>& parameters, map<Token, Node>& bindings) {
       return bindings[parameters[0]][3];
     }
+    
+    Function_Descriptor opacify_descriptor =
+    { "opacify", "$color", "$amount", 0 };
+    Function_Descriptor fade_in_descriptor =
+    { "fade_in", "$color", "$amount", 0 };
+    Node opacify(const vector<Token>& parameters, map<Token, Node>& bindings) {
+      Node cpy(bindings[parameters[0]].clone());
+      cpy[3].content.numeric_value += bindings[parameters[1]].content.numeric_value;
+      if (cpy[3].content.numeric_value >= 1) cpy[3].content.numeric_value = 1;
+      return cpy;
+    }
+    
+    Function_Descriptor transparentize_descriptor =
+    { "transparentize", "$color", "$amount", 0 };
+    Function_Descriptor fade_out_descriptor =
+    { "fade_out", "$color", "$amount", 0 };
+    Node transparentize(const vector<Token>& parameters, map<Token, Node>& bindings) {
+      Node cpy(bindings[parameters[0]].clone());
+      cpy[3].content.numeric_value -= bindings[parameters[1]].content.numeric_value;
+      if (cpy[3].content.numeric_value <= 0) cpy[3].content.numeric_value = 0;
+      return cpy;
+    }
       
     // String Functions ////////////////////////////////////////////////////
     

functions.hpp

@@ -77,6 +77,14 @@ namespace Sass {
     extern Function_Descriptor opacity_descriptor;
     Node alpha(const vector<Token>& parameters, map<Token, Node>& bindings);
     
+    extern Function_Descriptor opacify_descriptor;
+    extern Function_Descriptor fade_in_descriptor;
+    Node opacify(const vector<Token>& parameters, map<Token, Node>& bindings);
+    
+    extern Function_Descriptor transparentize_descriptor;
+    extern Function_Descriptor fade_out_descriptor;
+    Node transparentize(const vector<Token>& parameters, map<Token, Node>& bindings);
+    
     // String Functions ////////////////////////////////////////////////////
     extern Function_Descriptor unquote_descriptor;
     Node unquote(const vector<Token>& parameters, map<Token, Node>& bindings);