From: Robert Klemme <bob.news@...>
Date: 2004-07-07T20:47:39+09:00
Subject: Re: Array::index and rindex operator


"David A. Black" <dblack@wobblini.net> schrieb im Newsbeitrag
news:Pine.LNX.4.44.0407060917190.8001-100000@wobblini...
> Hi --
>
> On Wed, 7 Jul 2004, Robert Klemme wrote:
>
> > > > Might be best to just enhance #index with the block variant.
> > >
> > > What stumped me was: given this:
> > >
> > >   ary.index(x) {|e| <condition> }
> > >
> > > which behavior would you expect?  Or would it raise an exception?  I
> > > couldn't decide which would be best, which is what led me to a new
> > > method.
> >
> > #index simply returns nil.
>
> I think we're talking about different things.  What I meant is: if you
> extend/enhance #index to take a block, and then you give it a block
> *and* an argument, there's an ambiguity (two possible behaviors):
>
>   a = %w{ a b c d }
>   i = a.enhanced_index("b") {|x| x == "c" }
>
> Would i be 1 or 2?  Or would it raise an exception, because it's
> ambiguous?  (It's different from, say, #inject, where there's both an
> argument and a block but they have a direct connection with each
> other.)

I'd certainly have it throw an exception.

> My conclusion was that it would be better not to allow this to be
> legal, either by enforcing the choice in #index or creating a second
> method.

Yes, enforce the choice would be my preferred solution.

Regards

    robert