# Rustic Result

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Result monad for Elixir inspired by Rust
[Result](https://doc.rust-lang.org/std/result/) type.

## Installation

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

```elixir
def deps do
  [
    {:rustic_result, "~> 0.4.0"}
  ]
end
```

## Usage

```elixir
import Rustic.Result

ok(42) == {:ok, 42}
# true

err(:not_found) == {:error, :not_found}
# true

ok(42) |> is_ok?()
# true

err(:not_found) |> is_err?()
# true

ok(1) |> map(fn v -> v + 1 end)
# ok(2)

err(:not_found) |> map(fn v -> v + 1 end)
# err(:not_found)

ok(1) |> map_err(fn reason -> {:failed, reason} end)
# ok(1)

err(:not_found) |> map_err(fn reason -> {:failed, reason} end)
# err({:failed, :not_found})

ok(1) |> and_then(fn v -> ok(v + 1) end)
# ok(2)

ok(1) |> and_then(fn _ -> err(:not_found) end)
# err(:not_found)

err(:not_found) |> and_then(fn v -> ok(v + 1) end)
# err(:not_found)

ok(1) |> or_else(fn _ -> ok(2) end)
# ok(1)

err(:not_found) |> or_else(fn :not_found -> ok(1) end)
# ok(1)

err(:not_found) |> or_else(fn :not_found -> err(:invalid) end)
# err(:invalid)

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

err(:not_found) |> unwrap!()
# ** (Rustic.Result.UnhandledError) Expected an Ok result, ":not_found" given.

ok(1) |> unwrap_or(2)
# 1

err(:not_found) |> unwrap_or(2)
# 2

ok(1) |> unwrap_err!()
# ** (Rustic.Result.MissingError) Expected an Err result, "1" given.

err(:not_found) |> unwrap_err!()
# :not_found

ok(ok(1)) |> flatten()
# ok(1)

ok(err(:failed)) |> flatten()
# err(:failed)

ok(1) |> flatten()
# ok(1)

[ok(1), ok(2)] |> collect()
# ok([1, 2])

[ok(1), err(:not_found)] |> collect()
# err(:failed)

[ok(1), err(:not_found)] |> filter_collect()
# ok([1])

[ok(1), err(:not_found)] |> partition_collect()
# {ok([1]), err([:not_found])}
```