From: "baweaver (Brandon Weaver) via ruby-core" <ruby-core@...>
Date: 2024-11-09T03:21:21+00:00
Subject: [ruby-core:119859] [Ruby master Feature#20770] A *new* pipe operator proposal

Issue #20770 has been updated by baweaver (Brandon Weaver).


I'd written on the previous iteration of the pipeline operator a while ago here: https://dev.to/baweaver/ruby-2-7-the-pipeline-operator-1b2d

The ending example of what I thought, at the time, was an ideal state of it was:

```ruby
double = -> v { v * v }
increment = -> v { v + 1 }

5
|> double
|> increment
|> to_s(2)
|> reverse
|> to_i
```

...which mixed both methods and procs to effectively pretend that Ruby was a LISP-1 derivative language, if only for the sake of pipelines. I believe that given the LISP-2 nature of the language this would be confusing, and add complexity for not a lot of practical gain compared to the combination of `then` and `it`.

Frequently what folks are looking for is a nicer way to say this:

```ruby
def some_method(v) = v + 1

5.then(&method(:some_method))
```

...and there have been a few proposals in that spirit before like `.:`:

```ruby
HTTP.get(some_url).then(&JSON.:parse)
```

...which I still think is an interesting potential syntax, and when applied to some of the pipeline proposals may become something like this:

```ruby
HTTP.get(some_url)
  |> JSON.:parse
  |> filter { |k, v| v.is_a?(Integer) }
```

But again, comparatively speaking there's not a lot of overhead to `then` and `it` in those cases:

```ruby
HTTP.get(some_url)
  .then { JSON.parse(it) }
  .filter { |k, v| v.is_a?(Integer) }
```

...except to add more syntax that may be unclear for newer Ruby programmers that will be very hard to find documentation for. Even if I would very much like a shorter way to say `Object.method(:something)` I debate if it would be wise.

----------------------------------------
Feature #20770: A *new* pipe operator proposal
https://bugs.ruby-lang.org/issues/20770#change-110549

* 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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