This is possibly the best answer. I won't give any
other.
--- drieux <[EMAIL PROTECTED]> wrote:
>
> On Thursday, Jun 5, 2003, at 13:07 US/Pacific,
> Andrew Brosnan wrote:
> [..]
> >>>> my $hash = {};
> >>>>
> >>>> while (my $rows = $response->fetchrow_hashref){
> >>>> $hash->{$rows->{task_ID}} = $rows;
> >>>> }
> >>>
> >>> Why is hash declared as my $hash and not my
> %hash?
> >>> and how does the
> >
> > This creates an annonymous hash '{}' and stores a
> reference to that
> > hash
> > in $hash.
>
>
> As for solving -
> when to use a reference to a hash,
> vice declaring a hash itself.
>
> Some of it is merely 'art work' - but there is a
> useful
> practical distinction, is one planning to
> pass by 'value' or pass by 'reference' at
> any time in the life of the variable. { and/or
> all of the future refactorings of the code.... 8-) }
>
> One can have a large hash, and if you pass it by
> value
> then you have to put all of the key/value pairs onto
> the stack.
> While if you passed merely a reference to the hash,
> you
> will pass merely the singular reference itself.
>
>
> I just hacked something where I was not sure what
> the
> structure would really need to look like, so opted
> to
> merely declare
>
> my $struct;
> ....
> $struct->{$sname} = "src: $src_file open
> error:\n\t $!";
> ....
> $struct->{$sname} = "copy of $src_file ok";
> ...
>
> so technically the code does not WARN the coder that
> I plan to use it as a reference to a hash.... but
> looking
> at the various places where I used it, most perl
> coders
> would understand that it was merely a hash.
>
> I also do this sort of trick when I am planning to
> do
> strange return solutions:
>
> sub some_funktion
> {
> ....
> return undef unless($condition_one);
> ....
>
> return "that's not right" if $error_case ;
>
> $hash_ref;
> }
>
> hence I can 'know' a bit about what went on with
>
> my $got_back = some_funktion(@arglist);
>
> unless(defined($got_back)) {
> # condition_one not met
> ....
> }
>
> unless(ref($got_back)) {
> #
> # that's not right handle the error_case
> #
> }
>
> while(my ($k,$v) = each %$got_back))
> {
> #
> # here we deal with it just like it were a regular
> hash
> #
> }
>
>
> HTH....
>
> ciao
> drieux
>
> ---
>
>
> --
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