[ruby-talk:11004] Re: RubyChangeRequest #U002: new proper name for Hash#indexes, Array#indexes

On Sat, 17 Feb 2001, Mathieu Bouchard wrote:

> On Fri, 16 Feb 2001, David Alan Black wrote:
> > On Fri, 16 Feb 2001, Mathieu Bouchard wrote:
> > > Sorry, not really...
> > > a = [2,3,5,7]
> > > a[2]          #=> 5, one element in single mode
> > > a[2..2]	      #=> [5], one element in multiple mode
> > irb(main):001:0> a = [1,2,3,4]
> > [1, 2, 3, 4]
> > irb(main):002:0> a[1].type
> > Fixnum
> > irb(main):003:0> a[1..1].type
> > Array
> > I thought the proposed extension to #at would behave like that too -- ?
> 
> What do you mean, would behave like that? The proposed extension would
> make #at(*indices) return an array, but #at cannot distinguish a list of
> one element from a single value -- it's still a parameter list. There is
> no equivalent in the #[] realm, which can distinguish a one-element range
> from a single element fetch anytime.

I think part of the original discussion was whether to extend #at so
that it *did* behave differently when given more than one parameter:

  [1,2,3].at(0)       => 1
  [1,2,3].at(1,2)     => [2,3]

Mike Wilson had questioned whether the first of those two should
return a single value or an array:

  [1,2,3].at(0)       => [1]

Matz had said:

> For consistency, at(0) might be better to return an array, but it's
> incompatibility, which I don't want to incorporate.

I took this to mean consistency across all uses of (the extended) #at
-- namely, that the most consistent thing would be for it always to
return an array.

My subsequent point was that it might not actually be so inconsistent,
broadly taken, since there's a precedent for the idea of an array
fetch that returns a single value for a single-value fetch and an
array for a range-fetch: the current behavior of #[].

(I'm retracing this in hopes of, as usual, having the little lightbulb
go off... it isn't happening yet...  Of course, the little lightbulb
loves watching me hit the <send> button.... :-)


David

-- 
David Alan Black
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