From: artur.roszczyk@...
Date: 2018-02-05T17:39:20+00:00
Subject: [ruby-core:85409] [CommonRuby Feature#13581] Syntax sugar for	method reference

Issue #13581 has been updated by sevos (Artur Roszczyk).


Have we ruled out `map(&obj:method)` syntax? Intuitively I find it consistent with `Symbol#to_proc`

~~~ ruby
class Foo
  def initialize(array)
    @array = array
  end

  def call
    @array
      .map(&Math:sqrt)
      .map(&self:magic)
      .map(&self:boo(2.0))
      .map(&:ceil)
      .each(&Kernel:puts)
  end

  private

  def magic(x)
    x ** 3
  end

  def boo(a, b)
    a / b
  end
end
~~~

Alternatively, I am for triple colon:

~~~ ruby
class Foo
  def initialize(array)
    @array = array
  end

  def call
    @array
      .map(&Math:::sqrt)
      .map(&self:::magic)
      .map(&:::boo(2.0)) # with triple colon we could omit self
      .map(&:ceil)
      .each(&Kernel:::puts)
  end

  private

  def magic(x)
    x ** 3
  end

  def boo(a, b)
    a / b
  end
end
~~~

This could translate to:

~~~ruby
class Foo
  def initialize(array)
    @array = array
  end

  def call
    @array
      .map  { |x| Math.public_send(:sqrt, x) }
      .map  { |x| self.send(:magic, x) }
      .map  { |x| self.send(:boo, x, 2.0) }
      .map  { |x| x.ceil }
      .each { |x| Kernel.public_send(:puts, x) }
  end

  private

  def magic(x)
    x ** 3
  end

  def boo(a, b)
    a / b
  end
end
~~~

Applying additional arguments (aka `.map(&self:boo(2.0))` is just a proposal - I am not sure if this should be even possible - `Symbol#to_proc` does not allow that.

Another interesting question which we need to answer is:

**What visibility scope should be used when making a method call?**

Given the syntax `receiver:method` or `receiver:::method` if the receiver is `self` then we should expand this syntax sugar to `send()` allowing accessing the private interface of the current object (which is not the item from the iterator - we would use symbol to proc in that case). However, if the receiver is something else, we should expand to `public_send` to disallow accessing private methods of other objects.

Just my two cents ;)

Cheers,
Artur
 

----------------------------------------
Feature #13581: Syntax sugar for method reference
https://bugs.ruby-lang.org/issues/13581#change-70195

* Author: americodls (Americo Duarte)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
Some another programming languages (even Java, in version 8) has a cool way to refer a method as a reference.

I wrote some examples here: https://gist.github.com/americodls/20981b2864d166eee8d231904303f24b

I miss this thing in ruby.

I would thinking if is possible some like this:

~~~
roots = [1, 4, 9].map &Math.method(:sqrt)
~~~

Could be like this:

~~~
roots = [1, 4, 9].map Math->method
~~~

What do you guys thinking about it?



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