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Postings from January 2022
On Tue, 25 Jan 2022, 23:43 , <hv@crypt.org> wrote:
> yb@rslinux.fun wrote:
> :On Tue, Jan 25, 2022 at 01:20:17PM +0000, hv@crypt.org wrote:
> :> I think of local() as "temporarily replace the value at this lvalue
> :> with a new value, restore it at the end of the current lexical scope".
> :> This is hugely useful in many situations that would otherwise require
> :> more and slower code with much more opportunity for error.
> :
> :Out of curiosity, is there any reason not to simply shadow it: my $x =
> ...?
>
> In this case, it's an inline recursive function of which the relevant
> parts look a bit like:
>
> sub do_stuff {
> my $prod = 1;
> my $recurse;
> $recurse = sub {
> ...
> for my $new (@interesting_values) {
> local $prod = $prod * $new; # aspirational
> $recurse->();
> }
> };
> $recurse->();
> }
>
Just a minor nit, maybe not relevant, but that will leak.
I think the reason it's not allowed was local $x predates my $x. And it was
defined to operate on globals. But you could get the same result with a
global. Just rearrange the clauses a bit. Eg, add an our $prod outside the
outer sub. Then move and change your my $prod to right before the initial
call to $recurse as a local $prod.
You could fix the leakage and use globals for $prod by changing the recurse
to
our $prod;
local *recurse = sub {};
local $prod=1;
recurse();
Solving the leak this causes is the reason we created __SUB__
Yves
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