From: Trans <transfire@...>
Date: 2006-10-06T05:15:10+09:00
Subject: Re: Associating data with a function


Phrogz wrote:
> Trans wrote:
> > I look at this and think, "where the persistant locals?" Well, we don't
> > have em but they can be emulatated via instance vars.
> >
> >  class Foo
> >    def c1
> >      tmp1 = (@_tmp1 ||= ExpensiveObject.new)
> >      tmp2 = (@_tmp2 ||= ExpensiveObject.new)
> >      # stuff involving tmp1/tmp2
> >      result = tmp1 + tmp2 + c2
> >    end
> >    def c2
> >      tmp1 = (@_tmp1 ||= ExpensiveObject.new)
> >      tmp2 = (@_tmp2 ||= ExpensiveObject.new)
> >      # stuff involving tmp1/tmp2
> >      result = tmp1 + tmp2
> >    end
> >  end
>
> Persistent locals is an interesting concept. Your specific example
> fails, however, if I change c1's last line to:
>     result = tmp1 * c2 + tmp2
> because calculating c2 will change the value in @_tmp2, making the tmp2
> in c1 invalid. You'd need to ensure that each instance variable had a
> unique name in each function, which is just about the same as declaring
> all the instance variables during initialization or class creation.

Right, they should have had differnt names.

T.