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. On Wed, Sep 26, 2018 at 10:13:21AM -0400, Brandon Allbery wrote:
Not exactly that, but you can use groupBy fst . sort, then the head of the 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:
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...
but there are many cases where that's quite unhelpful. Actually what we 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...