Michael Lazzaro writes:<snip>Larry Wall wrote:We don't have a word for "START" right now. It's somewhat equivalent to state $foo //= 0
unless $foo gets undefined, I suppose.
Assuming we have a static-like scope called C<state>, one can
definitely see the use of having an assignment variant for "not yet
initialized" or "doesn't yet exist", the proposed spelling of which was
C<::=>.
I'm unconvinced by the need for a cryptic way to distinguish undefined from uninitialized.
Or, at least, if we want to make such a distinction here it should be because we come up with good examples where the distinction is useful, doing something that couldn't easily be achieved in some other way -- and that that usefulness is thought to outway the additional complexity of having another assignment operator in the language and having to distinguish it when teaching or learning Perl.
I suppose my own most common example is a hash representing a cache... it's entirely possible for C<undef> to be calculated and cached, but that doesn't mean the cache entry is invalid and should be recalculated every time -- a nonextant key would mean the cache entry is invalid.
{
$cache.{ $key } = $cache.load($key)
if not exists $cache.{ $key };
$cache.{ $key };
}In my own experiences, code similar to the above is awfully common. An assign-if-not-present form (at least for hashes, but in a magical fairy world, for arrays/params/whatever, too) such as:
$cache.{ $key } __= $cache.load($key);
would be a lot cleaner, and maybe a little faster, since it's testing C<$cache.{ $key }> once instead of -- what, 2.5 or 3 times, I guess, depending on how you count it?
Your mileage may vary, of course -- I must confess I need the undefined vs. noexists distinction all the time, but it's quite possible I code weirdly compared to other people. :-/
MikeL
