On Sun, Nov 9, 2014 at 11:07 PM, Raphaël Mongeau <raphaelsimeon@gmail.com> wrote:
This : 
pv a = [t | Just t <- pvc a]
is strange, can we really do pattern matching inside list comprehension?

Yes; that's part of the point of list comprehensions, and of their extension to (and, back in the very early days, contraction from) monad comprehensions.

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