From: Alex LeDonne <aledonne.listmail@...>
Date: 2007-01-23T00:36:56+09:00
Subject: Re: Hash pairs at?

On 1/21/07, Trans <transfire@gmail.com> wrote:
>
> dblack@wobblini.net wrote:
> > Hi --
> >
> > On Mon, 22 Jan 2007, Joel VanderWerf wrote:
> >
> > > gga wrote:
> > >> dblack@wobblini.net wrote:
> > >>
> > >>> It's not incorrect or buggy; that's the way Enumerable#find_all works.
> > >>> In addition to being Enumerables themselves, arrays serve as the
> > >>> common container for the results of lots of different Enumerables.
> > >>>
> > >>
> > >> Sorry, David, but I disagree.  It may not be buggy (as the bugginess is
> > >> properly documented :), but it is certainly incorrect.  Re-read my
> > >> post.
> > >> Hash.reject, which is also an Enumerable, DOES return a hash.
> > >> Hash.find_all which is algorithmically the same as Hash.reject but
> > >> without a negation, does not.
> > >> Someone forgot to override find_all in the Hash case, but did remember
> > >> to do it for Hash.reject.  Or, if you are of the belief that indeed
> > >> Enumerables should always return an array, Hash.reject was incorrectly
> > >> overridden when it shouldn't have been.
> > >
> > > This does look a bit odd...
> > >
> > > irb(main):001:0> h = {1=>3, 5=>7}
> > > => {5=>7, 1=>3}
> > > irb(main):002:0> h.reject {|k,v| k==1}
> > > => {5=>7}
> > > irb(main):003:0> h.select {|k,v| k==1}
> > > => [[1, 3]]
> >
> > A bit.  The funny thing, though, is that it of course makes it
> > possible to do either -- so the irregularity actually provides a kind
> > of resilience.  The consistent version, should it ever come into
> > being, will shut the door on one of them.
> >
> > I know that people don't want to do select { not } and so on... so
> > I can see that it's not really ideal.  But it's kind of fascinating
> > that "fixing" it, in either direction, would result in a net loss of
> > functionality.
>
> Avoiding net loss, how about going for gross gain. So how about "fixing
> it" so there is both?
>
>   select
>   select_pair
>
> And {meth}_pair could also work for assoc arrays too.
>
> T.
>

Maybe I'm late to the party, but instead of select_pair, I'd name the
method slice, analagous to Array#slice.