Exts.Basics

Extensions to the core Basics library.

on : (a -> b) -> (b -> b -> c) -> a -> a -> c

Run a function on two inputs, before doing something with the result. Can be useful for things like sorts. For example, compare (List.length a) (List.length b) can be written on List.length compare.

See also compareBy.

compareBy : (a -> comparable) -> a -> a -> Order

Like Basics.compare, with a custom function. For example:

compareBy Date.toTime earlyDate laterDate
--> LT

maxBy : (a -> comparable) -> a -> a -> a

Like Basics.max, but it works on non-comparable types by taking a custom function. For example:

maxBy Date.toTime earlyDate laterDate
--> laterDate

minBy : (a -> comparable) -> a -> a -> a

Like Basics.min, but it works on non-comparable types by taking a custom function. For example:

minBy Date.toTime earlyDate laterDate
--> earlyDate

module Exts.Basics exposing
    ( on
    , compareBy
    , maxBy
    , minBy
    )

{-| Extensions to the core `Basics` library.

@docs on
@docs compareBy
@docs maxBy
@docs minBy

-}


{-| Run a function on two inputs, before doing something with the
result. Can be useful for things like sorts. For example, `compare
(List.length a) (List.length b)` can be written `on List.length
compare`.

See also `compareBy`.

-}
on : (a -> b) -> (b -> b -> c) -> a -> a -> c
on f g a b =
    g (f a) (f b)


{-| Like `Basics.compare`, with a custom function. For example:

    compareBy Date.toTime earlyDate laterDate
    --> LT

-}
compareBy : (a -> comparable) -> a -> a -> Order
compareBy f =
    on f compare


{-| Like `Basics.max`, but it works on non-comparable types by taking a custom function. For example:

    maxBy Date.toTime earlyDate laterDate
    --> laterDate

-}
maxBy : (a -> comparable) -> a -> a -> a
maxBy toComparable x y =
    if compareBy toComparable x y == LT then
        y

    else
        x


{-| Like `Basics.min`, but it works on non-comparable types by taking a custom function. For example:

    minBy Date.toTime earlyDate laterDate
    --> earlyDate

-}
minBy : (a -> comparable) -> a -> a -> a
minBy toComparable x y =
    if compareBy toComparable x y == LT then
        x

    else
        y