From: "AlexandreMagro (Alexandre Magro) via ruby-core" <ruby-core@...>
Date: 2024-10-15T10:01:28+00:00
Subject: [ruby-core:119529] [Ruby master Feature#20770] A *new* pipe operator proposal

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


Reflecting on the opposing points raised, I believe the pipe operator could work differently, avoiding the issue of "implicit blocks" mentioned by @zverok.

As suggested by @Eregon, translating the operator to local variables reduces the overhead associated with chaining `.then`.

What I (re)propose is to define the pipe operator as a **statement separator**, similar to `;`, where `LHS` expression is evaluated first and its result is stored in the variable `_`, which we can call as "last expression result", and then `RHS` is executed.

For instance, this:

```ruby
expr_a |> expr_b
```

Would conceptually translates to:

```ruby
expr_a => _; expr_b
```

This way, we could write:

```ruby
"https://api.github.com/repos/ruby/ruby"
  |> URI.parse(_)
  |> Net::HTTP.get(_)
  |> JSON.parse(_)
  |> _.fetch("stargazers_count")
  |> puts "Ruby has #{_} stars"
```

This approach maintains clarity, avoids the overhead of multiple `.then` calls, and introduces the `_` variable as the last expression result, similar to the "ANS" button on a calculator.

----------------------------------------
Feature #20770: A *new* pipe operator proposal
https://bugs.ruby-lang.org/issues/20770#change-110143

* 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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