[Haskell-cafe] Matching constructors
Mark T.B. Carroll
mark at ixod.org
Fri Feb 10 13:26:45 EST 2006
Creighton Hogg <wchogg at primula.hep.wisc.edu> writes:
> data Patootie = Pa Int | Tootie Int
> and I want to pull out the indices of all elements of a list
> that have type constructor Tootie, how would I do that?
x = [Pa 3, Tootie 5, Pa 7, Tootie 9, Pa 11]
y = [ i | Tootie i <- x ]
z = [ i | i@(Tootie _) <- x ]
y or z might be helpful.
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