Sigh, I seem to have done a reply to sender. Reposting to the list. On 06/02/07, phiroc@free.fr <phiroc@free.fr> wrote:

Hello,

I would like to create a Haskell function that generates a truth table, for all Boolean values, say, using the following "and" function :

and :: Bool -> Bool -> Bool and a b = a && b

A fairly old thread, but I had an interesting idea:

combos :: (Enum a, Enum b) => a -> b -> (a -> b -> c) -> [(a, b, c)] combos min1 min2 op = [(x, y, x `op` y) | x <- [min1..], y <- [min2..]]

Then: *Main> combos False (&&) [(False,False,False),(False,True,False),(True,False,False),(True,True,True)] In the case of Bool and a few others, you can use a slightly nicer one:

bCombos :: (Enum a, Bounded a, Enum b, Bounded b) => (a -> b -> c) -> [(a, b, c)] bCombos op = [(x, y, x `op` y) | x <- [minBound..maxBound], y <- [minBound..maxBound]]

And: *Main> bCombos (&&) [(False,False,False),(False,True,False),(True,False,False),(True,True,True)] The secret of these is of course in the Enum and Bounded type classes, which define, respectively, * enumFrom and enumFromTo (which have syntactic sugar in [foo..] and [foo..bar] respectively), and * minBound and maxBound. You can do the same with any instance of these classes. -- Peter Berry <pwberry@gmail.com> Please avoid sending me Word or PowerPoint attachments. See http://www.gnu.org/philosophy/no-word-attachments.html