On Wed, May 27, 2009 at 7:05 AM, John Macdonald <j...@perlwolf.com> wrote:
> On Tue, May 26, 2009 at 04:38:21PM -0700, yary wrote:
>> perl4-perl5.8 or so had a variable that let you change the starting
>> index for arrays, so you could actually make the above work. But then
>> everyone who'd re-arranged their brains to start counting at 0, and
>> written code that has a starting index of 0, would have problems.
>
> That was $[ and it goes back to perl 1 or so. I recall
> experimenting with it a couple of times. Using it, though,
> means that you have to use $[ as the lower range limit for
> *every* array everywhere.
Is it still a global in Perl 6? I've noticed a trend toward using
less expansive scopes, so that setting $[ to 1 might mean that arrays
that are defined in the current scope are 1-based instead of 0-based,
whereas arrays defined in other scopes (such as inside a function
imported from a module) might continue to be 0-based.
> That gets stale very quickly, and I then decided that I would
> just never change the setting of $[ and would remove such a
> change from any code that I called.
...which is probably the cleanest way to handle it. It's for a
similar reason that postcircumfix:<[ ]> always uses $[-based
consecutive integers for indexing: you always have a consistent way of
referring to, e.g., "the first element" (@x[0]) or "the last element"
(@x[*-1]), without having to worry about which indexing scheme any
particular array might be using.
That's also the reason for custom indexing: if you _want_ to use
1-based indexing for a given array, you can always define a custom
index and then refer to the first element by saying "@x{1}'.
--
Jonathan "Dataweaver" Lang
