From: "AlexandreMagro (Alexandre Magro) via ruby-core" <ruby-core@...>
Date: 2024-11-12T19:02:34+00:00
Subject: [ruby-core:119904] [Ruby master Feature#20770] A *new* pipe operator proposal

Issue #20770 has been updated by AlexandreMagro (Alexandre Magro).


lpogic (��ukasz Pomiet��o) wrote in #note-46:
> I wonder if the pipeline operator with assignment wouldn't also be useful in everyday code:
> 
> ``` ruby
> str = "ABC"
> str |>= _.reverse
> str # => "CBA"
> 
> a_simple_json = '{"key":"value"}'
> a_simple_json |>= JSON.parse _
> a_simple_json # => {"key"=>"value"}
> 
> a = [{greeting: "Hello"}]
> a[0][:greeting] |>= "#{_} World!"
> a # => [{greeting: "Hello World!"}]
> ```

The pipe operator is well-known, but this type of operation with assignment is something I haven���t seen before, and I���m not sure of its precedence. The examples also don���t illustrate a strong need for it.

```ruby
# 1

str = "ABC".reverse

# 2

a_simple_json = JSON.parse '{"key":"value"}'
```

In the third example, a dedicated method would be more suitable, I believe a similar proposal was made here: https://bugs.ruby-lang.org/issues/20818

----------------------------------------
Feature #20770: A *new* pipe operator proposal
https://bugs.ruby-lang.org/issues/20770#change-110609

* 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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