fix to_s (mostly)

lib/ruby/statement.rb

@@ -24,8 +24,9 @@ module Ruby
     # helper method for formatting source code
     # depth is the depth in the tree (os the ast)
     # and the string are the ones to be indented (2 spaces)
-    def at_depth(depth , *strings)
+    def at_depth(depth , lines)
       prefix = " " * 2 * depth
+      strings = lines.split("\n")
       strings.collect{|str| prefix + str}.join("\n")
     end
   end