ruby-core

Issue #15799 has been updated by jonathanhefner (Jonathan Hefner).


Eregon (Benoit Daloze) wrote:

> Also, if we actually introduce a pipeline operator, I think it's much more useful to have Elixir semantics of passing the result as the first argument of the RHS, than just a different syntax for `.`.

I agree that the pipeline operator should introduce new semantics, instead of being an alias of `.`.

While Elixir uses `|>` to insert a first argument to the RHS, F# and Elm use `|>` to append a last argument to the RHS (due to different conventions regarding function parameter order).

One use-case for such "last argument" behavior in Ruby is file IO:

```ruby
File.read("file.txt").gsub(/foo/, "bar") |> File.write "file.txt"
```

Of course it gets tricky when option arguments are involved.  But perhaps kwargs could be handled specially, such that the LHS of `|>` is inserted before them.  For example, the following would both work as expected: 

```ruby
File.read("other.txt") |> File.write "file.txt", mode: "a"
```
```ruby
File.read("other.txt") |> File.write "file.txt", **options
```


----------------------------------------
Feature #15799: pipeline operator
https://bugs.ruby-lang.org/issues/15799#change-78084

* Author: nobu (Nobuyoshi Nakada)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
Implemented the pipeline operator `|>`, a topic of "ruby committers vs the world" in RubyKaigi 2019.
Also a casual idea of rightward assignment.

```ruby
1.. |> take 10 |> map {|x| x*2} |> (x)
p x #=> [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]
```

https://github.com/nobu/ruby/tree/feature/pipeline




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