From: "David A. Black" <dblack@...>
Date: 2004-07-06T21:26:09+09:00
Subject: Re: Array::index and rindex operator

Hi --

On Tue, 6 Jul 2004, Robert Klemme wrote:

> 
> "Kristof Bastiaensen" <kristof@vleeuwen.org> schrieb im Newsbeitrag
> news:pan.2004.07.06.10.51.04.229075@vleeuwen.org...
> > Hi,
> >
> > On Tue, 06 Jul 2004 09:42:41 +1000, George Ogata wrote:
> >
> > > Sometimes though I wish that #index could take a block (i.e., return
> > > the first index for which the block is true).  Unless I'm overlooking
> > > something, there doesn't seem to be a method that does this.  I don't
> > > know what others think of the idea, but that would probably go some
> > > way towards your goal.
> >
> > I think that would be nice.  I would vote for it.
> > You could do this with enumerator, but it is not so compact:
> >
> > require "enumerator"
> >
> > a = %w(one two three)
> > a.enum_for(:each_with_index).find { |s, i| s == "two" }[1]
> > => 1
> 
> Another solution:
> 
> a.inject(0) {|i,s| break i if "two" == s; idx+1}

The problem though (aside from 'idx' for 'i' :-) is that you always
get a number, even if there's no element found:

  [1,2,3].inject(0) {|i,s| break i if "two" == s; i + 1}

  # => 3


David

-- 
David A. Black
dblack@wobblini.net