The point is that %h[0] should be legal syntax that works on any hash,
returning the "first" element. It doesn't matter if the elements are
sorted or even sortable. You get an element. More to the point, if
you don't add any elements to (or remove any elements from) the hash,
you get the *same* element every time you ask for %h[0], which is
different from %h[1], etc - all this is by default, of course.
But is %h[0] a value or a pair? Or does it depend on context?
On 6/2/08, Jon Lang <[EMAIL PROTECTED]> wrote:
> David Green wrote:
>> Jon Lang wrote:
>>> Bear in mind that keys are not necessarily sortable, let alone
>>> autosorted.
>>> For instance, consider a hash that stores values keyed by complex
>>> numbers:
>>> since there's no way to determine .before or .after when comparing two
>>> complex numbers, there's no way to sort them - which necessarily means
>>> that
>>> the order of :v is arbitrary, making %h[0] arbitrary as well.
>>
>> Aha -- I guess you're thinking in terms of "autosorting" that can be
>> turned
>> on to return the values ordered by < and >.
>
> Not the values; the keys.
>
>> But .iterator can do whatever
>> it wants, which in the default case is presumably to walk a hash-table
>> (technically not an arbitrary order, although it might as well be as far
>> as
>> a normal user is concerned).
>
> ...which is my point. When I speak of "arbitrary order", I mean that
> the programmer should not be expected to know in what order the keys
> will be returned. As opposed to a "meaningful order", whereas the
> programmer can look at a set of the current keys and figure out which
> index corresponds with which key.
>
>>> This is why I was suggesting that it be limited to autosorted hashes:
>>> it's
>>> analogous to how @a{'x'} is only accessible if you've actually defined
>>> "keys" (technically, user-defined indices) for @a.
>>
>> Do you see that as a psychological aid? That is, if the order is
>> arbitrary,
>> %h[0] makes sense technically, but may be misleading to a programmer who
>> reads too much into it, and starts thinking that the order is meaningful.
>
> Something like that. Really, it's more about asking that the order
> _be_ meaningful before you start using array-style indices, since
> doing the latter carries the presumption of the former.
>
>> My feeling is that it's fine for all hashes to support []-indexing. But
>> if
>> the order isn't important, then you probably wouldn't need to use [] in
>> the
>> first place (you'd use "for %h:v", etc.)... so maybe it should be limited.
>> Hm.
>
> That's my thought. That said, I'm wiling to consider the prospect
> that such a restriction is excessive and/or unnecessary.
>
>> P.S. Everywhere I said < and > I really meant .before and .after. =P
>
> :) OK.
>
> --
> Jonathan "Dataweaver" Lang
>
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Mark J. Reed <[EMAIL PROTECTED]>
