Croma.ListMonad (croma v0.12.0)

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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]

Summary

Types

t(a)

Functions

ap(ma, mf)

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.

Types

t(a)

@type t(a) :: [a]

Functions

ap(ma, mf)

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

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)

@spec 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)

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

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)

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

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

sequence(list)

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

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.

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}