diff --git a/lib/typed/tree/assignment.rb b/lib/typed/tree/assignment.rb
index d8d12e26..99f4092b 100644
--- a/lib/typed/tree/assignment.rb
+++ b/lib/typed/tree/assignment.rb
@@ -5,6 +5,9 @@ module Typed
       def initialize(n = nil , v = nil )
         @name , @value = n , v
       end
+      def to_s
+        "#{name} = #{value}\n"
+      end
     end
   end
 end
diff --git a/lib/typed/tree/statements.rb b/lib/typed/tree/statements.rb
index aabe44f9..e72b4fa7 100644
--- a/lib/typed/tree/statements.rb
+++ b/lib/typed/tree/statements.rb
@@ -1,5 +1,9 @@
 module Typed
   class Statements < Statement
     attr_accessor :statements
+    def to_s
+      return "" unless statements
+      statements.collect() { |s| s.to_s }.join
+    end
   end
 end
diff --git a/lib/typed/tree/while_statement.rb b/lib/typed/tree/while_statement.rb
index e73602f9..69e7ac1d 100644
--- a/lib/typed/tree/while_statement.rb
+++ b/lib/typed/tree/while_statement.rb
@@ -4,7 +4,7 @@ module Typed
       attr_accessor :branch_type , :condition , :statements
       def to_s
         str = "while_#{branch_type}(#{condition}) do\n"
-        str + statements.join(" ") + "\nend\n"
+        str + statements.to_s + "\nend\n"
       end
     end
   end