From: Olivier Renaud <o.renaud@...>
Date: 2007-03-04T00:26:21+09:00
Subject: Re: define a function inside a method

Le samedi 03 mars 2007 16:10, Robert Klemme a �crit�:
> On 03.03.2007 15:41, Olivier Renaud wrote:
> > Hi,
> >
> > I wrote a method which uses recursion, internally. As a test, I tried to
> > define the recursive function inside the method that is called :
> >
> > class Ga
> >   def bu
> >     def zo(n)
> >       # recursively call zo
> >     end
> >   10.times {|n| zo(n)}
> > end
> >
> > At my surprise, this code ran well ! But I wonder if this is a good
> > idea... Should I be aware of possible problems, or limitations,  coming
> > from this kind of construction ? I can't figure out where the zo function
> > actually "lives".
>
> The issue here is (apart from the missing "end" in your piece above)
> that zo will be defined every time you execute bu - that's probably not
> something you want as it is inefficient and you do not actually change
> zu's definition.  Also, zo becomes a normal method - there is no such
> thing as a nested method in Ruby:
>
> irb(main):001:0> class Ga
> irb(main):002:1>   def bu
> irb(main):003:2>     def zo(n)
> irb(main):004:3>       # recursively call zo
> irb(main):005:3*     end
> irb(main):006:2>   10.times {|n| zo(n)}
> irb(main):007:2> end
> irb(main):008:1> end
> => nil
> irb(main):009:0> Ga.new.zo 1
> NoMethodError: undefined method `zo' for #<Ga:0x39ba98>
>          from (irb):9
>          from :0
> irb(main):010:0> Ga.new.bu
> => 10
> irb(main):011:0> Ga.new.zo 1
> => nil
>
> Kind regards
>
> 	robert

Thanks, this is perfectly clear !
Finally, I rewrote this method to avoid the recursion, since it was a tail 
recursion.

-- 
Olivier Renaud