Handling unary + and -. Makes more tests pass.

src/document_parser.cpp

@@ -655,6 +655,18 @@ namespace Sass {
       if (!lex< exactly<')'> >()) syntax_error("unclosed parenthesis");
       return value;
     }
+    else if (lex< exactly<'+'> >()) {
+      Node plus(Node::unary_plus, context.registry, line_number, 1);
+      plus << parse_factor();
+      plus.eval_me = true;
+      return plus;
+    }
+    else if (lex< exactly<'-'> >()) {
+      Node minus(Node::unary_minus, context.registry, line_number, 1);
+      minus << parse_factor();
+      minus.eval_me = true;
+      return minus;
+    }
     else {
       return parse_value();
     }

src/eval_apply.cpp

@@ -223,6 +223,26 @@ namespace Sass {
         return apply_function(f_env[sig], expr[1], env, f_env, registry);
       } break;
       
+      case Node::unary_plus: {
+        Node arg(eval(expr[0], env, f_env, registry));
+        if (arg.is_numeric()) return arg;
+        else {
+          expr[0] = arg;
+          return expr;
+        }
+      } break;
+      
+      case Node::unary_minus: {
+        Node arg(eval(expr[0], env, f_env, registry));
+        if (arg.is_numeric()) {
+          arg.set_numeric_value(-arg.numeric_value());
+        }
+        else {
+          expr[0] = arg;
+          return expr;
+        }
+      } break;
+      
       case Node::string_schema:
       case Node::value_schema: {
         cerr << "evaluating schema of size " << expr.size() << endl;

src/node.cpp

@@ -174,6 +174,20 @@ namespace Sass {
         return "/";
       } break;
       
+      case unary_plus: {
+        stringstream ss;
+        ss << "+";
+        ss << at(0).to_string("");
+        return ss.str();
+      }
+      
+      case unary_minus: {
+        stringstream ss;
+        ss << "-";
+        ss << at(0).to_string("");
+        return ss.str();
+      }
+      
       case numeric_percentage: {
         stringstream ss;
         ss << content.dimension.numeric_value;

src/node.hpp

@@ -59,6 +59,8 @@ namespace Sass {
       div,
 
       factor,
+      unary_plus,
+      unary_minus,
       values,
       value,
       identifier,
@@ -170,6 +172,21 @@ namespace Sass {
       }
     }
     
+    void set_numeric_value(double v)
+    {
+        switch (type)
+        {
+          case number:
+          case numeric_percentage:
+            content.numeric_value = v;
+          case numeric_dimension:
+            content.dimension.numeric_value = v;
+          default:
+            break;
+            // throw an exception?
+        }
+      }
+    
     Node& operator+=(const Node& n)
     {
       for (int i = 0; i < n.size(); ++i) {