From: "austin (Austin Ziegler) via ruby-core" <ruby-core@...>
Date: 2024-11-09T02:54:03+00:00
Subject: [ruby-core:119858] [Ruby master Feature#20770] A *new* pipe operator proposal

Issue #20770 has been updated by austin (Austin Ziegler).


lpogic (��ukasz Pomiet��o) wrote in #note-39:
> @austin, @AlexandreMagro I understand that this is a creature from the functional world. However, I wonder whether the current proposal (statement operator) would allow for such a forms:
> ``` ruby
> def foo
>   r |> (q_result = q(_)) |> p(_)
>   return q_result
> end
> # or
> def foo
>   r |> q_result = q(_) |> p(_)
>   return q_result
> end
> 
> def bar
>   (r_result = r) |> q(_) |> p(_, r_result)
> end
> ```

My opposition to this concept in #note-37 stands for the same reasons. This is unreadable and has indeterminate scope.

A pipeline operator is best used for passing the first parameter (like Elixir), the last parameter (some JavaScript `.pipe(���)` implementations; Go text templates), or an arbitrary parameter with an explicit marker (`it`, `_`, `_1`, etc.).

Ruby already *has*  pipeline-like method, `#then`. If `|>` or `.{}` acts as syntactic sugar for `#then`, I don't see an issue here. If, internally, it���s turned into the effective equivalent of `__pipe1 = r; __pipe2 = q(__pipe1); __pipe3 = p(__pipe2); __pipe3`, I don't see an issue here. But under no circumstances do I think that the effective temporary assignments should be exposed or made available to method calls further down the pipeline or after the pipeline is complete. That's too much magic.

----------------------------------------
Feature #20770: A *new* pipe operator proposal
https://bugs.ruby-lang.org/issues/20770#change-110548

* 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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