Proposal: Add chop function to Data.List
lennart at augustsson.net
Tue Dec 14 11:24:40 CET 2010
I don't really care if the function is called chop or not.
But in many cases it is used to chop a list into smaller pieces.
On Tue, Dec 14, 2010 at 12:00 AM, wren ng thornton <wren at freegeek.org>wrote:
> On 12/13/10 12:17 PM, Lennart Augustsson wrote:
>> I would like to propose the following function for inclusion in Data.List
>> chop :: ([a] -> (b, [a])) -> [a] -> [b]
>> chop _  = 
>> chop f as = b : chop f as'
>> where (b, as') = f as
>> It's commonly occuring recursion pattern. Typically chop is called
>> with some function that will consume an initial prefix of the list
>> and produce a value and the rest of the list.
>> The function is clearly related to unfoldr, but I find it more
>> convenient to use in a lot of cases.
> It's also deeply related to iteratees (for the obvious enumerator of a
> list). The major difference is that iteratees enforce that the consuming
> function must return a tail of the input stream, whereas this function
> doesn't require that at all (for both good and ill).
> The name "chop" seems a bit strange to me, but other than that it's a nice
> Live well,
> Libraries mailing list
> Libraries at haskell.org
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