From: "marcandre (Marc-Andre Lafortune)" <ruby-core@...>
Date: 2012-11-10T02:42:45+09:00
Subject: [ruby-core:49171] [ruby-trunk - Feature #6284] Add composition for procs


Issue #6284 has been updated by marcandre (Marc-Andre Lafortune).


+1 for #*

The symbol used in mathematics for function composition is a circle (���); the arrows are for the definitions of functions (like lambdas) only, so #<- or whatever make no sense to me.

Finally, the f ��� g(x) is defined as f(g(x)), so there is no argument there either.
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Feature #6284: Add composition for procs
https://bugs.ruby-lang.org/issues/6284#change-32723

Author: pabloh (Pablo Herrero)
Status: Feedback
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: 
Target version: 2.0.0


=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


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