[ruby-core:119362] [Ruby master Feature#20770] A *new* pipe operator proposal

["bkuhlmann (Brooke Kuhlmann) via ruby-core" <ruby-core@ml.ruby-lang.org>]

Issue #20770 has been updated by bkuhlmann (Brooke Kuhlmann).


For background, this has been discussed before:

- [15799](https://bugs.ruby-lang.org/issues/15799): This was implemented and then reverted.
- [20580](https://bugs.ruby-lang.org/issues/20580): This recently popped up as well.
- There are probably other issues that I'm forgetting about that have been logged on this subject.

Introducing `|>` as an operator that works like `#then` would be interesting and would be similar to how Elixir works, as Alexandre mentioned. This is also how [Elm](https://elm-lang.org) works where you can elegantly use `|>` or `<|` as mentioned in the [Operators](https://elm-lang.org/docs/syntax#operators) documentation.

I also use something similar to how Sean uses a `#pipe` method with a block but mostly by refining the `Symbol` class as documented [here](https://alchemists.io/projects/refinements#_call) in my [Refinements](https://alchemists.io/projects/refinements) gem.

Also, similar to what Sean is describing, I provide the ability to *pipe* commands together without using `|>` by using my [Pipeable](https://alchemists.io/projects/pipeable) gem which builds upon native function composition to nice effect. Here's a snippet:

``` ruby
pipe data,
     check(/Book.+Price/, :match?),
     :parse,
     map { |item| "#{item[:book]}: #{item[:price]}" }
```

In both cases (refining `Symbol` or using Pipeable), the solution works great and provides and implements what is described here using different solutions. All solutions are fairly performant but would be neat if the performance could be improved further if there was a way to optimize these solutions natively in Ruby.

----------------------------------------
Feature #20770: A *new* pipe operator proposal
https://bugs.ruby-lang.org/issues/20770#change-109974

* 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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