Dear cafe, I'm trying to prepare a naive definition of booleans, numbers and some helper functions such a way, so that definition in lambda-calculus can be used in a straightforward way in Haskell. I was caught in trouble quite soon during change of lambda-expressions to Haskell - defining prefn as a helper for prev. When using Haskell-ish if-then-else then there is no problem (the code commented out), while using defined if-then-else (mif), the type-checking fails, but just for this case! Other simple tests are OK for the mif. Do I need some extra option for type-checker, or is it a principal failure (infinite type is reported) - I'm running ghci 6.10.4.
mtrue x y = x mfalse x y = y
m0 f n = n m1 f n = f n m2 f n = f (f n)
msucc x g m = x g (g m) iszero m = m (\_ -> mfalse) mtrue
mif c t f = c t f mpair f s = \e -> e f s mfst p = p mtrue msnd p = p mfalse
-- mprefn f p = if mex True False then mth else mel mprefn f p = mif mex mth mel where mex = mfst p mth = mpair mfalse (msnd p) mel = mpair mfalse (f (msnd p))
Please, change of definitions is not a solution, I'm trying to follow available resources, so using something else is not an option. :-( Thanks for any help Dusan