Rustic Maybe View Source

Maybe monad for Elixir inspired by Rust Option type.

Installation

This package can be installed by adding rustic_maybe to your list of dependencies in mix.exs:

def deps do
  [
    {:rustic_maybe, "~> 0.1.0"}
  ]
end

Usage

import Rustic.Maybe

some(1) == {:some, 1}
# true

nothing() == :nothing
# true

some(1) |> unwrap!()
# 1

nothing() |> unwrap!()
# ** (ArgumentError) trying to unwrap an empty Maybe monad

some(1) |> map(fn n -> n + 1 end)
# some(2)

nothing() |> map(fn n -> n + 1 end)
# nothing()

some(1) |> and_then(fn n -> some(n + 1) end)
# some(2)

nothing() |> and_then(fn n -> some(n + 1) end)
# nothing()

some(1) |> or_else(fn -> some(2) end)
# some(1)

nothing() |> or_else(fn -> some(2) end)
# some(2)

some(1) |> filter(fn n -> n > 0 end)
# some(1)

some(-1) |> filter(fn n -> n > 0 end)
# nothing()

nothing() |> filter(fn n -> n > 0 end)
# nothing()

For more examples, please consult the API reference.

With function guards:

import Rustic.Maybe

def handle_option(val) when is_nothing(val) do
  # ...
end
def handle_option(val) when is_some(val) do
  # ...
end
def handle_result(val) do
  raise ArgumentError, message: "#{inspect(val)} is not a Maybe monad"
end

Usage with Rustic.Result

Rustic.Result is an implementation of the Result monad, inspired by Rust's Result type.

Result.Maybe does not depend on Rustic.Result but can still work with its data type:

alias Rustic.Result  # if you installed it
alias Rustic.Maybe

Maybe.some(1) |> Maybe.ok_or(:no_value) == Result.ok(1)
# true

Maybe.nothing() |> Maybe.ok_or(:no_value) == Result.err(:no_value)
# true

Maybe.some(Result.ok(1)) |> Maybe.transpose() == Result.ok(Maybe.some(1))
# true

Maybe.some(Result.err(:no_value)) |> Maybe.transpose() == Result.err(:no_value)
# true

Maybe.nothing() |> Maybe.transpose() == Result.ok(Maybe.nothing())
# true

For more examples, please consult the API reference.