[Haskell-cafe] Re: Pattern matching articles/explanations

Aaron Denney wnoise at ofb.net
Thu Aug 16 17:29:37 EDT 2007

On 2007-08-16, Neil Mitchell <ndmitchell at gmail.com> wrote:
> Hi
>> So what I noticed that "A Gentle Introduction to Haskell" mentioned
>> that wild-cards are useful in constructors. For example:
>> head (x:_) = x
>> So, does that offer any performance benefits over:
>> head (x:xs) = x
> No. They are exactly the same. _ simply means "a new unique name".
>> Or is it primarily to indicate to the coder that xs is useless?
> Yes

And to the compiler that the name won't be used, so it needn't warn you
about not using it.

Aaron Denney

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