Implement lt operator for Number class

Author: mgreter

ast.cpp

@@ -1186,6 +1186,23 @@ namespace Sass {
     return operator==(&rhs);
   }
 
+  bool Number::operator< (Number* rhs) const
+  {
+    Number tmp_r(*rhs);
+    tmp_r.normalize(find_convertible_unit());
+    string l_unit(unit());
+    string r_unit(tmp_r.unit());
+    if (!l_unit.empty() && !r_unit.empty() && unit() != tmp_r.unit()) {
+      error("cannot compare numbers with incompatible units", pstate());
+    }
+    return value() < tmp_r.value();
+  }
+
+  bool Number::operator< (Number& rhs) const
+  {
+    return operator<(&rhs);
+  }
+
   bool String_Quoted::operator== (Expression* rhs) const
   {
     if (String_Quoted* qstr = dynamic_cast<String_Quoted*>(rhs)) {

ast.hpp

@@ -1192,6 +1192,8 @@ namespace Sass {
     // useful for making one number compatible with another
     string find_convertible_unit() const;
 
+    virtual bool operator< (Number& rhs) const;
+    virtual bool operator< (Number* rhs) const;
     virtual bool operator== (Expression& rhs) const;
     virtual bool operator== (Expression* rhs) const;