From: "shuber (Sean Huber) via ruby-core" <ruby-core@...>
Date: 2024-09-30T04:27:22+00:00
Subject: [ruby-core:119341] [Ruby master Feature#20770] A *new* pipe operator proposal

Issue #20770 has been updated by shuber (Sean Huber).


I would still love to see this type of pipeline functionality implemented with plain expressions instead of new operators.

I have this (old) working [proof of concept](https://github.com/lendinghome/pipe_operator#-pipe_operator) gem from years ago (basic syntax described below) but it was primarily focused on constant interception. I imagine it can be quite a bit more complex adding support for calling Proc objects and other edge cases.

```ruby
"https://api.github.com/repos/ruby/ruby".pipe do
  URI.parse
  Net::HTTP.get
  JSON.parse.fetch("stargazers_count")
  yield_self { |n| "Ruby has #{n} stars" }
  Kernel.puts
end
#=> Ruby has 22120 stars

-9.pipe { abs; Math.sqrt; to_i } #=> 3

[9, 64].map(&Math.pipe.sqrt.to_i.to_s) #=> ["3", "8"]
```

Most of the logic in that proof of concept was related to intercepting method calls to ALL constants which wouldn't be necessary if it was a core part of the language. The actual "pipeline" functionality (`PipeOperator::Pipe` and `PipeOperator::Closure`) is pretty simple - basically just keeping an array of constant+method+args calls and `reduce`ing the result when the pipeline ends.

The proof of concept is basically `prepend`ing a version of every method in every constant with something like the example below in order to support this "pipeline expressions" syntax:

```ruby
define_method(method) do |*args, &block|
  if Pipe.open
    Pipe.new(self).__send__(method, *args, &block)
  else
    super(*args, &block)
  end
end
```

https://github.com/lendinghome/pipe_operator#-pipe_operator

----------------------------------------
Feature #20770: A *new* pipe operator proposal
https://bugs.ruby-lang.org/issues/20770#change-109952

* 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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