[Haskell-cafe] A brief note on n_k patterns and Hackage

Don Stewart dons at galois.com
Tue May 5 21:57:20 EDT 2009

> On 5 May 2009, at 8:30 pm, Magnus Therning wrote:
>> On Tue, May 5, 2009 at 1:04 AM, Richard O'Keefe <ok at cs.otago.ac.nz>  
>> wrote:
>>> I never really understood why it was thought to be relevant,
>>> but I was challenged to show that n+k patterns occurred in
>>> Hackage.
>> Why is it relevant?
> Some people think that the popularity of a feature in
> an openly accessible collection of Haskell sources is
> relevant to whether it should continue to be supported,
> in a way that, say, appearance in textbooks, utility
> to beginners, and contribution to readability are not.
> Apparently.

    This was the main reason it was kept in Haskell 98, 11 years ago.
    New textbooks don't use it (RWH doesn't talk or recommend the use of n+k)
> I don't understand this.  n+k patterns are the ONLY
> Haskell98 feature scheduled for removal from Haskell'.

    For multiple reasons, summarised here:


-- Don    

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