Issue #6284 has been updated by Paul Mucur.

File 0001-proc.c-Implement-Proc-for-Proc-composition.patch added
File 0002-proc.c-Implement-Method-for-Method-composition.patch added

Attached patches for `Proc#*` and `Method#*` for Proc and Method composition including test cases. Also raised as a pull request on GitHub at https://github.com/ruby/ruby/pull/935

One thing that might be worth discussing is the necessity of the type checking: should it be possible to compose any callable object (rather than explicitly `Proc`s and `Method`s)? This could be deferred to a later enhancement as I imagine it would complicate the implementation.

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Feature #6284: Add composition for procs
https://bugs.ruby-lang.org/issues/6284#change-52925

* Author: Pablo Herrero
* Status: Feedback
* Priority: Normal
* Assignee: Yukihiro Matsumoto
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=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--------------------------------
0002-proc.c-Implement-Method-for-Method-composition.patch (2.71 KB)
0001-proc.c-Implement-Proc-for-Proc-composition.patch (3.73 KB)


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