Re: [Haskell-cafe] list comprehension with multiple generator|targets

On 11/10/2014 03:10 AM, Raphaël Mongeau wrote:

I don't think list comprehension is the solution. What you want is a map.

Would this work?

data V = A | B | C

f :: [V] -> String f l = flip map l $ \x -> case x of A -> 'A' B -> 'B' C -> 'C'

Looks like the job for LambdaCase, ‘flip map l $ \case …’ Also it doesn't do what the OPs function does because it doesn't skip C.

main = print $ f [A,B,C,C,A]

2014-11-09 21:58 GMT-05:00 Donn Cave :

...

I'm guessing this isn't supported, but might be worth asking - can I extend a list comprehension like ['A' | A <- s] to multiple values? Like,

data V = A | B | C

pv :: [V] -> [Char] pv [] = [] pv (A:x) = 'A':(pv x) pv (B:x) = 'B':(pv x) pv (_:x) = pv x

-- can that be a list comprehension, like

pv s = [ 'A' | A <- s -- ?? ]

thanks, Donn

-- Mateusz K.