From: Mauricio Fernandez <mfp@...>
Date: 2006-06-16T16:26:12+09:00
Subject: Re: Symbol#to_proc Problem

On Fri, Jun 16, 2006 at 10:40:48AM +0900, Elliot Temple wrote:
> it doesn't work for reversing arrays:
> 
> curi-g5:~ curi$ ruby -v
> ruby 1.8.4 (2005-12-24) [powerpc-darwin8.5.0]
> 
> irb(main):017:0> class Symbol
> irb(main):018:1>   def to_proc
> irb(main):019:2>     Proc.new { |obj, *args| obj.send(self, *args) }
> irb(main):020:2>   end
> irb(main):021:1> end
> => nil
> irb(main):022:0> [[1,2,3], [4,5,6], [7,8,9]].map {|i| i.reverse}
> => [[3, 2, 1], [6, 5, 4], [9, 8, 7]]
> 
> irb(main):023:0> [[1,2,3], [4,5,6], [7,8,9]].map &:reverse
> NoMethodError: undefined method `reverse' for 1:Fixnum
>         from (irb):19:in `send'
>         from (irb):19:in `to_proc'
>         from (irb):23
>         from (null):0

FYI the "official" implementation, recently added to Ruby 1.9, works that
way too:

$ ./ruby19 -v -e "p [[1,2,3], [4,5,6], [7,8,9]].map(&:reverse)"
ruby 1.9.0 (2006-06-11) [i686-linux]
-e:1: undefined method `reverse' for 1:Fixnum (NoMethodError)
        from -e:1

I read that Minero Aoki was against this being added to the core[1]; maybe it
was for the reason you exposed.


[1] http://mput.dip.jp/mput/?date=20060611#p01
-- 
Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby