Data.List.select

[Christian Maeder]

Dan Doel wrote:
> On Thursday 26 February 2009 5:36:05 am Christian Maeder wrote:
>> Libraries-List,
>>
>> browsing through the sources of Data.List I discovered "select", which
>> is only used for the implementation of partition and not exported.
>>
>> Can someone explain, why the irrefutable pattern "~" is used? Both
>> components are used in both branches.
> 
> To see the difference, go into ghci, and define select without the irrefutable 
> pattern. Then run the following:
> 
>   foldr (select even) ([],[]) [1..]

Cool!
Thanks, Christian