Re: Proposal for containers: Add 'pop' function to Data.Map

so it's uninsert (re uncons). - Oleg On 6.12.2020 21.41, Simon Jakobi via Libraries wrote:

Regarding the type signature:

pop :: Ord k => k -> Map k a -> (Maybe a, Map k a)

I think it might be better to be consistent with similar functions like

minView :: Map k a -> Maybe (a, Map k a)

and

uncons :: [a] -> Maybe (a, [a])

Therefore the type should be

pop :: Ord k => k -> Map k a -> Maybe (a, Map k a)

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I like the "pop" name though – I think the analogy to stacks is pretty obvious.

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Like Andreas Abel I believe, that if there is a good, simple implementation, it might be a good first step to simply document the implementation as an example.

If there's much demand for exporting the function or if a fast implementation is more complex, we can still enhance the API later on.

Am So., 6. Dez. 2020 um 17:20 Uhr schrieb Martijn Bastiaan via Libraries :

...

Hi all,

Proposal:

* Add `pop` and `popWithDefault` to `Data.Map` and `Data.IntMap`. * See https://github.com/haskell/containers/pull/757 for exact definition

Why:

* They're useful functions I expected to be in `Data.Map` and `Data.IntMap`. (This might be influenced by the fact that they're defined on Python's `dict`.)

* Their implementations (~ `updateLookupWithKey (\_ _ -> Nothing)`) are harder to parse than a simple `pop`, which should help Haskell codebases become a bit cleaner :).

* Their implementations are a bit non-obvious. My first instinct was to write `(Map.lookup ..., Map.delete ...)`, which would have done two traversals. Having "properly" implemented functions in the lib would prevent people from writing their own suboptimal ones.

Details and implementation:

* https://github.com/haskell/containers/pull/757

Kind regards, Martijn Bastiaan _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

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