cat/monad

Monad type {minimal implementation - bind}.

Types

Monad

Monad type.

class Applicative m => Monad m where
  (>>=) :: m a -> (a -> m b) -> m b

This type contains the Functor map function which can be calculated by default through the new function. Just like Haskell’s do notation, Gleam has use expressions that act as syntactic sugar:

// Haskell
sum :: Maybe Int
sum = do
  x <- Just 1
  y <- Just 2 
  return x + y


// Gleam
fn sum() -> Option(Int) {
  use x <- option_monad().bind(Some(1))
  use y <- option_monad().bind(Some(2))
  option_monad().return(x + y)
}

pub type Monad(m, a, b, ma, mb) {
  Monad(
    return: fn(a) -> ma,
    bind: fn(ma, fn(a) -> mb) -> mb,
    map: fn(ma, fn(a) -> b) -> mb,
  )
}

Constructors

Monad(
  return: fn(a) -> ma,
  bind: fn(ma, fn(a) -> mb) -> mb,
  map: fn(ma, fn(a) -> b) -> mb,
)

Values

new

</>

pub fn new(
  return: fn(a) -> ma,
  return2: fn(b) -> mb,
  bind bind: fn(ma, fn(a) -> mb) -> mb,
) -> Monad(m, a, b, ma, mb)

Constructor that provides a default map function.

fmap f mx = bind(mx)(\x -> return(f(x)))

to_functor

</>

pub fn to_functor(
  m: Monad(f, a, b, ma, mb),
) -> functor.Functor(f, a, b, ma, mb)

Functor instance from Monad.