[Haskell-beginners] How to avoid evaluating the second (undefined) argument of a Boolean AND operation?
Felipe Almeida Lessa
felipe.lessa at gmail.com
Thu Jun 23 01:21:55 CEST 2011
On Wed, Jun 22, 2011 at 8:07 PM, Jack Henahan <jhenahan at uvm.edu> wrote:
> myAND F _ = F
> instead of using x.
Actually that doesn't change anything and both definitions are the
same thing. The problem here is that "type checking is not lazy" =).
The second argument of myAND in "myAND F (1/0)" isn't being evaluated
at all; actually your code isn't running at all. What is being
reported is a type error, not a runtime error. Try one of these
myAND F undefined
myAND F (error "foo")
myAND F (let x = x in x)
myAND F (unsafePerformIO $ launchMissiles)
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