I've just debugged a program that used a case expression, but where I was trying to match on constants rather than literals. Here's a contrived example:
module Main where one = 1 two = 2
test n = case n of one -> "one" two -> "two" _ -> "three"
main = putStrLn (test 2)
This initial version seems to me to be the "natural" way to write the case expression, but it doesn't work because the first alternative always succeeds. This is what I've turned it into to get it to work. It seems a bit clumsy; is there a better way to write this?
test n = case True of _ | n == one -> "one" | n == two -> "two" | otherwise -> "three"
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