Re: [Haskell-cafe] Partial pattern matching

9 Mar 2009


      Peter Verswyvelen wrote:
...
In Haskell, a data constructor can be used partially applied:
data Pair a b = P a b
f = P 1
however, I cannot do "partial pattern matching", e.g
firstCoord (P x) = x
does not work.
I guess a very important reason must exist why this is the case?
What would be the type of firstCoord?


Typically, you'd use

data Pair a b = P { firstCoord :: a
		  , secondCoord :: b
		  }

or

firstCoord (P x _) = x
secondCoord (P _ y) = y


Regards,

-- 
Jochem Berndsen | jochem@functor.nl
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