One possible way to generate the values would be using a generic function for permutation with repetition, such as:

permuteRep :: [a] -> [b] -> [[(a,b)]]
permuteRep [] _ = []
permuteRep (a:[]) bs = [ [ (a,b) ] | b <- bs ]
permuteRep (a:as) bs = concat [ [ (a,b):p | p <- permuteRep as bs ] | b <- bs ]

and then use:

lines = permuteRep ["x","y","z"] [False,True]

In case the variable names can be discarded (or, in this case, not generated ... lazy evaluation rox ;-), then:

map (map snd) lines

This avoids having to provide a "domain" for each variable in the list comprehension, which could be problematic when dealing with many variables

On 2/21/07, Joe Thornber <joe.thornber@gmail.com> wrote:

> On 2/10/07, Peter Berry <pwberry@gmail.com> wrote:
> Prelude> putStrLn $ concatMap (flip (++)"\n") $ map show $ [(x,y,(&&) x y)
> |x <- [True,False],y <- [True,False]]

This can be simplified slightly to:

Prelude > putStrLn . unlines . map show $ [(x, y, x && y) | x <-
[True, False], y <- [True, False]]

- Joe
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