From: "David A. Black" <dblack@...>
Date: 2004-07-07T01:28:35+09:00
Subject: Re: Array::index and rindex operator

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.)

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.  


David

-- 
David A. Black
dblack@wobblini.net