Re: [Haskell-cafe] Where is "minimumsBy"?

Ah, right... Sorry. On Wed, Sep 26, 2018, 10:38 AM Bob Ippolito wrote:

Haskell’s sort algorithm is linear complexity when only evaluating the front of the list. See also https://ro-che.info/articles/2016-04-02-descending-sort-haskell which includes some measurements.

On Wed, Sep 26, 2018 at 10:30 David Feuer wrote:

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Laziness does not make the complexity work out fine. Sorting is still O(n log n), which isn't needed here.

On Wed, Sep 26, 2018, 10:22 AM Tom Ellis < tom-lists-haskell-cafe-2017@jaguarpaw.co.uk> wrote:

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Hopefully laziness makes the complexity work out fine. Nonetheless I don't like relying on laziness for the correct complexity and it would still be nice to have an explicit version.

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Not exactly that, but you can use groupBy fst . sort, then the head of

On Wed, Sep 26, 2018 at 10:13:21AM -0400, Brandon Allbery wrote: the

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result list is your "minimumsBy" result.

On Wed, Sep 26, 2018 at 6:28 AM Tom Ellis < tom-lists-haskell-cafe-2017@jaguarpaw.co.uk> wrote:

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Data.List.minimumBy :: Foldable t => (a -> a -> Ordering) -> t a -> a

https://www.stackage.org/haddock/lts-12.1/base-4.11.1.0/Data-List.html#v:min...

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but there are many cases where that's quite unhelpful. Actually

what we

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want is more like

minimumsBy :: ... => (a -> a -> Ordering) -> t a -> [a]

There can be many distinct minimizers. For example when I want to get the collection of the youngest people from [(Age, Person)] I want

minimumsBy (compare `on` fst) [(12, alice), (15, balaji), (12, cho)]

to return

[(12, alice), (12, cho)]

Does "minimumsBy" exist somewhere reasonably standard? Hoogle doesn't throw up anything obvious

https://www.stackage.org/lts-12.1/hoogle?q=%28a+-%3E+a+-%3E+Ordering%29+-%3E...

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