cat/bifunctor

Bifunctor type {minimal implementation - bimap}.
Default functions: first and second (defined in terms of bimap).
Bifunctor composition.

Types

Bifunctor

</>

Bifunctor type in gleam.

// Haskell type class
class Bifunctor f where
    bimap :: (a -> c) -> (b -> d) -> f a b -> f c d
    first :: (a -> c) -> f a b -> f c b
    first g = bimap g id
    second :: (b -> d) -> f a b -> f a d
    second = bimap id

pub type Bifunctor(f, a, b, c, d, fab, fcd) {
  Bifunctor(bimap: fn(fn(a) -> c, fn(b) -> d) -> fn(fab) -> fcd)
}

Constructors

Bifunctor(bimap: fn(fn(a) -> c, fn(b) -> d) -> fn(fab) -> fcd)

Values

bifunctor_compose

</>

pub fn bifunctor_compose(
  bf_instance: Bifunctor(bf, fua, gub, fuc, gud, bifgab, bifgcd),
  fu_instance: functor.Functor(fu, a, c, fua, fuc),
  gu_instance: functor.Functor(gu, b, d, gub, gud),
) -> Bifunctor(
  types.BiCompF(bf, fu, gu),
  a,
  b,
  c,
  d,
  bifgab,
  bifgcd,
)

Composition of a Bifunctor with 2 Functors.

// Haskell instance
instance (Bifunctor bf, Functor fu, Functor gu) =>
    Bifunctor (BiComp bf fu gu) where
        bimap f1 f2 (BiComp x) = BiComp ((bimap (fmap f1) (fmap f2)) x)

Examples

Right(Identity(3))
|> bifunctor_compose(either_bifunctor(), const_functor(), identity_functor())
  .bimap(fn(_) { panic }, fn(x) { x % 2 == 0 })
// -> Right(Identity(False))

first

</>

pub fn first(
  bifunctor: Bifunctor(f, a, b, c, b, fab, fcb),
) -> fn(fn(a) -> c) -> fn(fab) -> fcb

Default function first for a given Bifunctor instance.

Examples

let first_show =
    int.to_string
    |> {
        pair_bifunctor()
        |> first
    }

first_show(Pair(8, 9))
// -> Pair("8", 9)

second

</>

pub fn second(
  bifunctor: Bifunctor(f, a, b, a, d, fab, fad),
) -> fn(fn(b) -> d) -> fn(fab) -> fad

Default function second for a given Bifunctor instance.

Examples

let second_show = second(either_bifunctor())(int.to_string)

Left(8)
|> second_show
// -> Left(8)
Right(9)
|> second_show
// -> Right("9")