From: Christoph <chr_news@...>
Date: 2002-08-09T05:23:08+09:00
Subject: Re: Enumerable#any? (was: Re: Coding challenge (on Ruby Garden) [long])


<dblack@candle.superlink.net> wrote
....
> > Yup, they are a generalization of  && and || to Enumerables.
> >
> > module Enumerable
> >     def all?
> >         each {|e| return false unless yield e }
> >         return true
> >     end
> >     def any?
> >         each {|e| return true if  yield e }
> >          return false
> >     end
> > end
>
> At first glance I thought that #any? didn't add anything to just using
> the Boolean value of the result of #detect... until I tried this:

Hm, the #detect method was new to me;-)

>
>   ar = [1,2,3,nil,5]
>   puts "nil found by any?" if ar.any? {|e| e == nil }
>   puts "nil found by detect" if ar.detect {|e| e == nil}

In some sense

module Enumerable
    def all?
        last = true
        each {|e| return e unless last = yield e }
        return last
    end
   def any?
        last = nil # or false?
        each { |e| return e if last = yield e }
        return last
   end
end

might have been a better (but sort of useless;-)  generalization
of  Ruby's shortcut logic for && and ||.


/Christoph