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Postings from January 2022
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->();
}
.. so shadowing doesn't help. Alternatives such as a) making it a
one-element array, b) passing it as an argument or c) manually
saving and restoring are all possible, but all likely to be slower,
more error-prone, and add complexity to already-complex code.
The real code's aim is to find new values for https://oeis.org/A292580.
It's very much a work-in-progress, but if you're interested look at
https://github.com/hvds/seq/blob/master/divrep/oul#L167 for current
implementation (as one-element array).
Hugo
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