adds class definition with tests

lib/ast/module_expression.rb

@@ -30,5 +30,7 @@ module Ast
     end
   end
 
-  
+  class ClassExpression < ModuleExpression
+
+  end
 end

lib/parser/crystal.rb

@@ -31,6 +31,6 @@ module Parser
     include Operators
     include ModuleDef
 
-    rule(:root){ (module_definition | function_definition | expression  | call_site ).repeat }
+    rule(:root){ (module_definition | class_definition | function_definition | expression  | call_site ).repeat }
   end
 end

lib/parser/module_definition.rb

@@ -5,5 +5,11 @@ module Parser
       keyword_module >> name >> eol >>
       ( (keyword_end.absent? >> root).repeat(1)).as(:module_expressions) >> keyword_end >> newline
     end
+
+    rule(:class_definition) do
+      keyword_class >> name >> eol >>
+      ( (keyword_end.absent? >> root).repeat(1)).as(:class_expressions) >> keyword_end >> newline
+    end
+
   end
 end

lib/parser/transform.rb

@@ -53,8 +53,12 @@ module Parser
       Ast::OperatorExpression.new( o.to_s.strip , l ,r)
     end
     
+    #modules and classes are undertsndibly quite similar   Class < Module
     rule( :name => simple(:name) , :module_expressions => sequence(:module_expressions) , :end=>"end") do
-      Ast::ModuleExpression.new(name , module_expressions) 
+      Ast::ModuleExpression.new(name , module_expressions)
+    end
+    rule( :name => simple(:name) , :class_expressions => sequence(:class_expressions) , :end=>"end") do
+      Ast::ClassExpression.new(name , class_expressions)
     end
     
     #shortcut to get the ast tree for a given string