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Postings from April 2022
On Fri, 01 Apr 2022 09:54:37 -0400
"Ricardo Signes" <perl.p5p@rjbs.manxome.org> wrote:
> Item 5 is good. We should try to eliminate the need for "magic true
> value" in v5.38, generally.
Indeed; I think last time when we discussed the previous iteration of
the idea ("module"), we said that overall everything can be already
solved by the `use VERSION` and `package NAME VERSION {BLOCK}` features
that already exist in Perl and have done for a very long time, apart
from two small additions of:
* A mechanism (maybe attribute?) to request per-function lexical
exporting.
* A named feature that causes the .pm file as a whole to yield a true
value at the end.
I forget what we called them but those could be spelled:
use feature qw(export_attr yield_true);
package Some::Module v1.23 {
sub this_is_exported :export { ... }
sub this_method_is_not { ... }
my sub this_is_lexically_private { ... }
}
# no need for "1;" here because of the yield_true feature
That can all work *right now* with the `package` keyword. Furthermore,
the two new features, once implemented, could become part of a
`use VERSION` bundle at some future version of perl, so you could
simply write
use v5.100; # has already enabled strict, warnings, signatures and
# yield_true; has disabled indirect, etc...
package Some::Module v1.23 {
sub f :export ($x, $y) { ... }
}
Looking further over the (closed) PR from last time:
https://github.com/Perl/RFCs/pull/11
What I said was:
@Ovid I think the :export attribute could stand alone well in its own
RFC. Do you want to write one up, or should I?
A couple of further thoughts on it:
* Perl core already reserves all the lowercase attribute names for
its own future expansion. There's no need to use feature-guard it.
We can add `:export` right now.
* I think the named tags should take a leading colon; e.g.
`:export(:strings)`. That way they visually match what the
`use Module ':strings';` import line looks like, and also it gives
us some space to put other options in there one day.
I would definitely be in favour of seeing (two?) RFCs to specifically
add these ideas:
1. An :export attribute for lexical exports (see quoted PR comment
above)
2. A `use feature 'yield_true'` to avoid having to put "1;" at the end
of the file; with a future plan to include that by default in the
versioned feature bundles.
I believe that combination, plus a proper understanding of how
`use VERSION` and `package NAME VERSION {BLOCK}` already work in Perl,
will fully cover the use-cases and benefits of your proposed "library"
keyword, without the need for new keywords or a significant departure
of existing Perl syntax.
--
Paul "LeoNerd" Evans
leonerd@leonerd.org.uk | https://metacpan.org/author/PEVANS
http://www.leonerd.org.uk/ | https://www.tindie.com/stores/leonerd/
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