24 Jan
2010
24 Jan
'10
4:12 p.m.
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