From: Hugh Sasse Staff Elec Eng <hgs@...>
Date: 2003-12-04T05:04:22+09:00
Subject: Re: each_with_what_index?

On Thu, 4 Dec 2003, David A. Black wrote:

> Hi --
>
> On Thu, 4 Dec 2003, Hugh Sasse Staff Elec Eng wrote:
>
> > Suppose if each_with_index allowed a range parameter
> >    a.each_with_index(1...a.size) {|t,i|...}
> > Would that be worth an RCR?  It looks sort of natural to me, but...
>
> Just for fun:
>
>   module Enumerable
>     def each_with_index(range=(0...size))
>       range.each {|i| yield at(i),i}
>     end
>   end

Easier than I thought.
>
> though it doesn't do much for me.  I guess I haven't seen the problem
> to which it would be a solution, and it seems to be based on a sort of

One place it could be used is with one array indexing k others,
where the indices are sorted based on {whatever happens to be of
interest}.   But it is anything that responds_to?(each) so there may
be more applications than are dreamt of in my philosophy...

> rollback of the original request (i.e., here's a enumerable; give me
> its elements and their indices; wait, actually, don't act on the
> receiver but on a subsequent restraint...).  It feels inside-out to
> me.

Do act on the receiver but...
"I want this book printed, but just the odd pages (then I'll feed them
through again)..."

I think that was almost how the problem was framed:  "I want all the
elements, well, except the zeroth, of course!".

It does make it easier to change your mind about which ones, later.
>
>
> David
> --
> David A. Black
> dblack@wobblini.net
>

        Hugh