From: "jeremyevans0 (Jeremy Evans) via ruby-core" <ruby-core@...>
Date: 2024-09-30T22:55:54+00:00
Subject: [ruby-core:119369] [Ruby master Feature#20770] A *new* pipe operator proposal

Issue #20770 has been updated by jeremyevans0 (Jeremy Evans).


AlexandreMagro (Alexandre Magro) wrote in #note-9:
> Yes, and it's also possible to achieve this with a chain of `.then`, which results in a similar structure. The idea of the pipe operator is to be syntactic sugar, bringing functionality from functional languages into Ruby without introducing any complexity, while maintaining ruby's simplicity.
> 
> ```ruby
> client_api_url
>   .then { URI.parse(it) }
>   .then { Net::HTTP.get(it) }
>   .then { JSON.parse(it).fetch(important_key) }
> ```

We could expand the syntax to treat `.{}` as `.then{}`, similar to how `.()` is `.call()`.  With that, you could do:

```ruby
client_api_url
  .{ URI.parse(it) }
  .{ Net::HTTP.get(it) }
  .{ JSON.parse(it).fetch(important_key) }
```

Which is almost as low of a syntatic overhead as you would want.

Note that we are still in a syntax moratorium, so it's probably better to wait until after that is over and we have crowned the one true parser before seriously considering new syntax.

----------------------------------------
Feature #20770: A *new* pipe operator proposal
https://bugs.ruby-lang.org/issues/20770#change-109982

* 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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