Re: A better type signature for `forM_`

1 Apr 2016


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Erik de Castro Lopo  writes:
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As pointed out to me on IRC (thanks pjdeport), chaning the type signature of
`forM_` to
    forM_' :: (Monad m, Foldable t) => t a -> (a -> m ()) -> m ()
would have resulted in an error.
What about mapM_, replicateM_, etc.? In each case, '_' means "if you return a
value from your action, it is ignored", and not "you must return unit".

-- 
John Wiegley                  GPG fingerprint = 4710 CF98 AF9B 327B B80F
http://newartisans.com                          60E1 46C4 BD1A 7AC1 4BA2