[ruby-core:77534] [Ruby trunk Feature#6284] Add composition for procs

Issue #6284 has been updated by Alexander Moore-Niemi.


I wrote a gem with a C extension of `Proc#compose`: https://github.com/mooreniemi/proc_compose#usage

What motivated me was `map f (map g xs) = map (f . g) xs`, and what I still don't understand (being a newbie to extending Ruby or understanding its internals) is that `.map(&some_proc).map(&some_other_proc)` still behaves better than `.map(&(some_proc * some_other_proc))` given my current implementation of `compose`. Although I think composition has a lot of uses, the admittedly small but free performance benefit I expected to gain was top of my list.

I do think emphasis on composition suggests a somewhat different style of writing Ruby, but I think it can be a good one, actually.

Paul: what's the performance of your `compose`? If I have time later I can use https://github.com/mooreniemi/graph-function to try and see.

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Feature #6284: Add composition for procs
https://bugs.ruby-lang.org/issues/6284#change-60805

* Author: Pablo Herrero
* Status: Feedback
* Priority: Normal
* Assignee: Yukihiro Matsumoto
----------------------------------------
=begin
It would be nice to be able to compose procs like functions in functional programming languages:

    to_camel = :capitalize.to_proc
    add_header = ->val {"Title: " + val}

    format_as_title = add_header << to_camel << :strip

instead of:

    format_as_title = lambda {|val| "Title: " + val.strip.capitalize }


It's pretty easy to implement in pure ruby:

  class Proc
    def << block
      proc { |*args| self.call( block.to_proc.call(*args) ) }
    end
  end
=end

---Files--------------------------------
0001-proc.c-Implement-Proc-for-Proc-composition.patch (3.65 KB)
0002-proc.c-Implement-Method-for-Method-composition.patch (2.67 KB)
0003-proc.c-Support-any-callable-when-composing-Procs.patch (3.97 KB)


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