croma v0.11.0 Croma.ListMonad View Source

Implementation of Croma.Monad interface for built-in lists.

This empowers the following Haskell-ish syntax for loops using lists:

iex> use Croma
...> Croma.ListMonad.m do
...>   i <- [1, 2, 3]
...>   j <- [10, 20]
...>   pure i + j
...> end
[11, 21, 12, 22, 13, 23]

Link to this section Summary

Default implementation of Applicative's ap operation. Modules that implement Croma.Monad may override this default implementation. Note that the order of arguments is different from the Haskell counterpart, in order to leverage Elixir's pipe operator |>.

bind(l, f)

Implementation of bind operation of Monad. Alias to Enum.flat_map/2.

m(list)

A macro that provides Hakell-like do-notation.

map(ma, f)

Default implementation of Functor's fmap operation. Modules that implement Croma.Monad may override this default implementation. Note that the order of arguments is different from the Haskell counterpart, in order to leverage Elixir's pipe operator |>.

pure(a)

Implementation of pure operation of Monad (or Applicative). Wraps the given value into a list.

sequence(list)

Converts the given list of monadic (to be precise, applicative) objects into a monadic object that contains a single list. Modules that implement Croma.Monad may override this default implementation.

Link to this section Types

t(a)

t(a) :: [a]

Link to this section Functions

ap(ma, mf)

ap(t(a), t((a -> b))) :: t(b) when a: any(), b: any()

bind(l, f)

bind(t(a), (a -> t(b))) :: t(b) when a: any(), b: any()

Implementation of bind operation of Monad. Alias to Enum.flat_map/2.

m(list)

(macro)

A macro that provides Hakell-like do-notation.

Examples

MonadImpl.m do
  x <- mx
  y <- my
  pure f(x, y)
end

is expanded to

MonadImpl.bind(mx, fn x ->
  MonadImpl.bind(my, fn y ->
    MonadImpl.pure f(x, y)
  end)
end)

map(ma, f)

map(t(a), (a -> b)) :: t(b) when a: any(), b: any()

pure(a)

pure(a) :: t(a) when a: any()

Implementation of pure operation of Monad (or Applicative). Wraps the given value into a list.

sequence(list)

sequence([t(a)]) :: t([a]) when a: any()

Examples (using Croma.Result)

iex> Croma.Result.sequence([{:ok, 1}, {:ok, 2}, {:ok, 3}])
{:ok, [1, 2, 3]}

iex> Croma.Result.sequence([{:ok, 1}, {:error, :foo}, {:ok, 3}])
{:error, :foo}