Doesn't the simply typed lambda calculus introduce if-then-else as a primitive precisely so that it can be typed?
Its not an illuminating answer to your question and I'd welcome clarification for my own understanding, but I don't think you can solve the problem without appealing to Haskell's built-in if-then-else. Best wishes Stephen _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
