From: hemant <gethemant@...>
Date: 2006-10-19T11:41:13+09:00
Subject: Re: whats this lambda code doing?

On 10/19/06, Morton Goldberg <m_goldberg@ameritech.net> wrote:
> On Oct 18, 2006, at 9:12 PM, Ezra Zygmuntowicz wrote:
>
> >
> > On Oct 18, 2006, at 6:02 PM, David Vallner wrote:
> >
> >> Ezra Zygmuntowicz wrote:
> >>>    klasses.inject(block) do |blk, klass|
> >>>      lambda { klass.with_scope(scope_hash, &blk) }
> >>>    end.call
> >>>
> >>> That outer block that ends on end returns the lambda made inside
> >>> of that
> >>> block. So end.call ends up being  lambda { klass.with_scope
> >>> (scope_hash,
> >>> &blk) }.call
> >>>
> >>
> >> Hmm. Unless I'm very mistaken, it would also only call the lambda for
> >> the last object in klasses, generating several garbage (and
> >> relatively
> >> expensive) lambdas. Boggle. Am I missing something?
> >>
> >> David Vallner
> >
> >       It looks like it would only call the last lambda but it does call
> > all of them. Here is a simplification of whats happening.
> >
> > irb(main):065:0>  def scoper(klasses=[:foo, :bar, :baz], &block)
> > irb(main):066:1>    klasses.inject(block) do |blk, klass|
> > irb(main):067:2*      lambda { puts klass; blk.call}
> > irb(main):068:2>    end.call
> > irb(main):069:1>  end
> > => nil
> > irb(main):070:0* scoper { puts '&block called' }
> > baz
> > bar
> > foo
> > &block called
> > => nil
> > irb(main):071:0>
>
> I think I'm still confused by this. I infer from your post that the
> lambdas get nested by the inject (at the position of 'blk') with the
> first one innermost, which is why they get called in reverse order
> (and 'block' last of all). Is that right?
>
> Regards, Morton
>
>

Hmm...i think i get the idea, but i do not understand how its .call is
working on all the lambdas?


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