`return` takes a single argument. You've given it 3 and 2 arguments in your two uses.

Dean

Thanks Dean it help me a lot. i'm not used to program in Haskell i usualy program in Java, C, Prolog and Delphi. I'm implementing a Prolog Interpreter in Haskell in a University Discipline. that's why i have this newby questions about Haskell. p.s.- sorry about my english i don't write in english for a while.