From: Jacob Fugal <lukfugl@...>
Date: 2006-04-20T02:30:40+09:00
Subject: Re: Symbol#to_proc is just so beautiful

On 4/19/06, Berger, Daniel <Daniel.Berger@qwest.com> wrote:
> > -----Original Message-----
> > From: Daniel Schierbeck [mailto:daniel.schierbeck@gmail.com]
> >
> > When is this ever getting into Ruby Core?
> >
> >    class Symbol
> >      def to_proc
> >        proc{|obj| obj.send(self) }
> >      end
> >    end
> >
> > Consider this:
> >
> >    class Numeric
> >      def positive?
> >        self > 0
> >      end
> >    end
> >
> >    [1, 2, 3].all? &:positive?  => true
> >    [-1, 2, 3].all? &:positive? => false
>
> There must be a way to ditch that '&' somehow.  I'd prefer this:
>
> [1,2,3].all?(:positive?)

It's possible be adjusting the definition of Enumerable#all?

  $ cat test.rb
  class Symbol
    def to_proc
      proc{ |obj| obj.send(self) }
    end
  end

  module Enumerable
    alias :old_all? :all?

    def all?(non_block=nil, &block)
      if non_block
        if block.nil? and non_block.respond_to?(:to_proc)
          block = non_block.to_proc
        else
          raise ArgumentError
        end
      end
      old_all? &block
    end
  end

  class Numeric
    def positive?
      self > 0
    end

    def even?
      (self % 2).zero?
    end
  end

  puts [1, 2, 3].all?
  puts [1, 2, 3].all? { |i| i < 4 }
  puts [1, 2, 3].all? { |i| i > 2 }
  puts [1, 2, 3].all?( :positive? )
  puts [1, 2, 3].all?( :even? )

  $ ruby test.rb
  true
  true
  false
  true
  false

I'm not sure if there's anyway to do it without redefining the target
function, however.

Jacob Fugal