start to add while loop

lib/parser/conditional.rb

@@ -6,5 +6,10 @@ module Parser
         delimited_expressions(keyword_else).as(:if_true) >> 
         delimited_expressions(keyword_end).as(:if_false)
     }
+    
+    rule(:while) {
+      keyword_while  >> expression.as(:while_cond) >>  keyword_do >> newline >> 
+                        delimited_expressions(keyword_end).as(:body)
+    }
   end
 end

lib/parser/keywords.rb

@@ -8,5 +8,8 @@ module Parser
     rule(:keyword_true) {   str('true').as(:true) >> space?}
     rule(:keyword_false){   str('false').as(:false) >> space?}
     rule(:keyword_nil)  {   str('null').as(:nil) >> space?}
+    rule(:keyword_while)  {   str('while').as(:while) >> space?}
+    rule(:keyword_do)  {   str('do').as(:do) >> space?}
+    rule(:keyword_begin)  {   str('begin').as(:begin) >> space?}
   end
 end

lib/parser/transform.rb

@@ -24,6 +24,11 @@ module Parser
            Ast::ConditionalExpression.new(conditional, if_true, if_false) 
          end
 
+    rule(:while     => simple(:while), :while_cond => simple(:while_cond) , :do => simple(:do), 
+         :body => {:expressions => sequence(:body)}) do
+           Ast::WhileExpression.new(while_cond, body) 
+         end
+
     rule(:parmeter  => simple(:parmeter))    { parmeter  }
     rule(:parmeter_list => sequence(:parmeter_list)) { parmeter_list }