From: Trans <transfire@...>
Date: 2007-11-11T07:02:43+09:00
Subject: Re: equivalent injecting implementations?



On Nov 10, 10:50 am, "Rick DeNatale" <rick.denat...@gmail.com> wrote:
> On Nov 10, 2007 9:37 AM, Trans <transf...@gmail.com> wrote:
>
>
>
> > On Nov 10, 8:50 am, "Rick DeNatale" <rick.denat...@gmail.com> wrote:
> > > On 11/9/07, Trans <transf...@gmail.com> wrote:
>
> > > > Are these strictly equivalent? I get the feeling no, but I haven't
> > > > been able to demonstrate it yet.
>
> > > >   def injecting(s)
> > > >     inject(s) do |k, i|
> > > >       yield(k, i); k
> > > >     end
> > > >   end
>
> > > >   def injecting(res, &block)
> > > >     ([res]*length).zip(to_a).each(&block)
> > > >     res
> > > >   end
>
> > > > Thanks,
> > > > T.
>
> > > I can't see how in general they can be.
>
> > > In which class or module are you defining these?  Since you are using
> > > inject and each, I'm guessing that it's either Enumerable or some
> > > subclass,
>
> > > But then depending on which subclass you don't have a length method so...
>
> > > Perhaps some more context would help.
>
> > Oh sorry, I meant to put that. These are Enumerable methods.
>
> module Enumerable
>   def injecting(s)
>      inject(s) do |k, i|
>        yield(k, i); k
>      end
>    end
>
>    def injecting2(res, &block)
>      ([res]*length).zip(to_a).each(&block)
>      res
>    end
>  end
>
> (1..3).injecting(0) {|k,i| k + i} # => 0
> (1..3).injecting2(0) {|k,i| k + i} # =>
> # ~> -:9:in `injecting2': undefined local variable or method `length'
> for 1..3:Range (NameError)
> # ~>         from -:15
>
> Which illustrates my point.

Ah. sorry. I missed what you were getting at there. Yea, right off the
bat length isn't support, so it would have to apply to Array instead.
I was really just curious how they differ in result because they were
outputing the same thing when I rand some cases on it.

> Just what is injecting supposed to mean anyway? The first
> implementation uses inject and takes a two argument block like inject
> does, but seems to be going out of it's way to disregard the value of
> the argument block.
>
> This doesn't seem much like inject to me.

It's basically the the same, but you don't need to pass the memo back
each time.

T.