On Tue, 29 Aug 2000 20:21:39 +0800, Kenneth Lee wrote:
>oday this just came up to my mind, we could have a pragma that disable
>`autovivification' of hash and array keys. Consider the follow code snippet:
>
> @arr = ( 0..9 );
> %hash = ( a=>1, b=>2 );
>
> {
> no autovivify;
> $arr{10}++; # both are
> $hash{c}--; # fatal
> }
>
>this way we can eliminate the need to tie any variables to special classes
>and catch invalid accesses.
Would it? Hmmm... One of the problems is with fields of, for example,
objects. There, not just autovivification, but simply access of a
nonexistent field should cause a complaint. That is a problem that your
proposal doesn't solve.
But, there's at least one function where I would want to disable
autovivification: for parameters to exists().
Witness:
use Data::Dumper;
unless(exists $hash{foo}{bar}{baz}{quux}) {
print "Nope.\n";
}
print Dumper \%hash;
-->
Nope.
$VAR1 = {
'foo' => {
'bar' => {
'baz' => {}
}
}
};
This pollution of my data structures can be pretty annoying. I'd like
this not to ever happen.
Perhaps this should even be extended to all data accesses not in a LHS
context.
--
Bart.
