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AlistairB/interesting-monad.hs

Created April 22, 2017 00:03
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I found it surprising how this worked :) But it helped me understand monads and do
Raw
interesting-monad.hs
twiceWhenEven :: [Integer] -> [Integer]
twiceWhenEven xs = do
x <- xs
if even x
then [x*x, x*x]
else [x*x]
-- Prelude> twiceWhenEven [1..3]
-- [1,4,4,9]
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