From: "ufuk (Ufuk Kayserilioglu) via ruby-core" <ruby-core@...>
Date: 2024-09-30T22:15:49+00:00
Subject: [ruby-core:119367] [Ruby master Feature#20770] A *new* pipe operator proposal

Issue #20770 has been updated by ufuk (Ufuk Kayserilioglu).


AlexandreMagro (Alexandre Magro) wrote in #note-7:
> With the pipe operator, the same logic can be simplified and made more readable:
> 
> ```
> client_api_url
>   |> URI.parse(it)
>   |> Net::HTTP.get(it)
>   |> JSON.parse(it).fetch(important_key)
> ```

I would like to note that this almost works already today:
```ruby
irb> client_api_url = "https://jsonplaceholder.typicode.com/posts/1"
#=> "https://jsonplaceholder.typicode.com/posts/1"

irb> pipeline = URI.method(:parse) >> Net::HTTP.method(:get) >> JSON.method(:parse)
#=> #<Proc:0x000000012c62b4e8 (lambda)>

irb> pipeline.call(client_api_url)
#=>
{"userId"=>1,
 "id"=>1,
 "title"=>"sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
 "body"=>
  "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"}

irb> pipeline = URI.method(:parse) >> Net::HTTP.method(:get) >> JSON.method(:parse) >> -> { it.fetch("title") }
#=> #<Proc:0x000000012c4c2778 (lambda)>

irb> pipeline.call(client_api_url)
#=> "sunt aut facere repellat provident occaecati excepturi optio reprehenderit"

```

You can also make the whole pipeline with just using procs:
```ruby
(-> { URI.parse(it) } >> -> { Net::HTTP.get(it) } >> -> { JSON.parse(it) } >> -> { it.fetch("title") }).call(client_api_url)
#=> "sunt aut facere repellat provident occaecati excepturi optio reprehenderit"
```
which is much closer to the syntax that you want, except for the lambda wrappers.

I think with `Proc#>>` and `Proc#<<` this need for chaining is mostly in place already. The thing that is really missing is the ability to access a method by name without having to do `.method(:name)` which was proposed in https://bugs.ruby-lang.org/issues/16264. That proposal would make the first example be:
```ruby
(URI.:parse >> Net::HTTP.:get >> JSON.:parse >> -> { it.fetch("title") }).call(client_api_url)
#=> "sunt aut facere repellat provident occaecati excepturi optio reprehenderit"
```
which looks much nicer.

----------------------------------------
Feature #20770: A *new* pipe operator proposal
https://bugs.ruby-lang.org/issues/20770#change-109980

* Author: AlexandreMagro (Alexandre Magro)
* Status: Open
----------------------------------------
Hello,

This is my first contribution here. I have seen previous discussions around introducing a pipe operator, but it seems the community didn't reach a consensus. I would like to revisit this idea with a simpler approach, more of a syntactic sugar that aligns with how other languages implement the pipe operator, but without making significant changes to Ruby's syntax.

Currently, we often write code like this:

```ruby
value = half(square(add(value, 3)))
```

We can achieve the same result using the `then` method:

```ruby
value = value.then { add(_1, 3) }.then { square(_1) }.then { half(_1) }
```

While `then` helps with readability, we can simplify it further using the proposed pipe operator:

```ruby
value = add(value, 3) |> square(_1) |> half(_1)
```

Moreover, with the upcoming `it` feature in Ruby 3.4 (#18980), the code could look even cleaner:

```ruby
value = add(value, 3) |> square(it) |> half(it)
```

This proposal uses the anonymous block argument `(_1)`, and with `it`, it simplifies the code without introducing complex syntax changes. It would allow us to achieve the same results as in other languages that support pipe operators, but in a way that feels natural to Ruby, using existing constructs like `then` underneath.

I believe this operator would enhance code readability and maintainability, especially in cases where multiple operations are chained together.

Thank you for considering this proposal!






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