# Ok Jose
A tiny library for piping function return
values on a given pattern like the erlang
idiom `{:ok, _}` and `{:error, _}` tuples.
You can also define your own pattern-matched
pipes besides `ok` and `error`.
## Motivation
A lot of erlang libraries follow the
convention of returning `{:ok, _}` and
`{:error, _}` tuples to denote success or failure.
This library is my try at having a beautiful syntax for a *happy pipe*, that is, a pipe that expects `{:ok, _}` tuples to be returned by each piped function.
If any piped function returns a non matched value, the remaining functions expecting an `{:ok, _}` value wont get executed.
So, for example, the following code
```elixir
filename
|> File.read()
|> case do
{:ok, content} ->
content |> Poison.Parser.parse()
{:error, _} = error -> error
end
```
can be written as:
```elixir
filename |> File.read |> Poison.Parser.parse |> ok
```
## Usage
```elixir
use OkJose
```
Provides you with the following macros:
`ok`, `ok!`, `error`, `error!`
```elixir
use OkJose.Pipe
```
which provides you the `defpipe` macro.
#### `ok`
Pipes values into functions as long as they match `{:ok, _}`
```elixir
{:ok, v} |> f |> g |> ok
```
#### `ok!`
Pipes values into functions but if at any point a value
does not match `{:ok, _}` raises a match error.
#### `defpipe`
Allows you to define custom pipe patterns, for example
the previous `ok`, `ok!` macros are defined like:
```elixir
defpipe ok(value <- {:ok, value})
defpipe ok!(value <- {:ok, value})
```
## Example
```elixir
def dup(x), do: {:ok, x * 2}
def nop(x), do: {:error, x}
12 |> dup |> dup |> ok # => {:ok, 48}
24 |> nop |> dup |> ok # => {:error, 24}
24 |> dup |> ok! # => 48
24 |> nop |> dup |> ok! # raises
```
## Installation
1. Add ok to your list of dependencies in `mix.exs`:
```elixir
def deps do
[{:ok_jose, "~> 0.0.1"}]
end
```
## About ok
I wanted name this library `ok`, but the `hex`
package name was [already taken](https://hex.pm/packages/ok). So I just wanted to make a
tribute to @josevalim.
Actually both projects are trying to solve the
same issue. But I think this one has an easier
syntax that consist of just piping to `ok`
## Is it any good?
[Yes](https://news.ycombinator.com/item?id=3067434)