From: Victor Deryagin <vderyagin@...>
Date: 2011-05-28T15:20:21+09:00
Subject: Re: Problem in using %:whatever in enumumerations

RichardOnRails <RichardDummyMailbox58407@USComputerGurus.com> writes:

> Hi,
>
> I'm on  a Ruby self-improvement mission.  Presently I working my way
> though all 47 of the Enumerable methods in Ruby 1.9.2.  I composed the
> following:
>
> greek = %w{Alpha Beta Gamma}
> puts greek.all? { |s| s.length == 5 }		#  (correct)  => false
> puts greek.all? { |s| (4..5).include? s.length }	#  (correct)  => true
> puts greek.all?(&:length)			#  (programmer error)     => true
>
> The last line is programmed incorrectly because I couldn't stick in
> the intended "5" in a syntactically correct way.  Is the most
> effective way construction of a lamda/proc? If so, how?
>
> Thanks in advance,
> Richard:

& converts method with a given name to Proc object, for example:

    &:length

 becomes:

    { |s| s.length }

If that's not what you want (e.g. you need { |s| s.length == 5 }) -
construct block yourself. There is no way to specify arguments when
 using &:length.