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Postings from January 2017
On Fri, 08 Oct 2010 13:29:35 GMT, timbo wrote: > > This is a bug report for perl from Tim.Bunce@pobox.com, > generated with the help of perlbug 1.39 running under perl 5.12.2. > > > ----------------------------------------------------------------- > [Please describe your issue here] > > [16:05] timbunce: code like "if ref $foo" is far more expensive than > it needs to be because ref() still creates a new SVPV when called in a > boolean context. > [16:08] xdg: timbunce, could you please open a ticket on that? I'm > sure someone can optimize that. > [16:10] • Nicholas wonders if "if ref $foo" can be spotted with much > the same code as "if %hash" is > [16:10] Zefram: yes it can, at op check time > [16:11] timbunce: How can internals determine "boolean context"? > [16:11] vincent: at op check time > [16:11] timbunce: there are probably other ops that could do less work > in boolean context > [16:11] Nicholas: offhand, "I don't know", but I know that "if %hash" > does this > > [16:11] Zefram: but ref($foo)'s truth value isn't as simple as most > people expect, so it's approximately never what a programmer actually > wants > [16:12] timbunce: Zefram: true, but that doesn't stop people writing > "if ref $foo" often > [16:13] Zefram: I'd be more inclined to use check-time logic to emit a > warning for it > [16:14] Zefram: "Dubious use of reference-type operator in truth-value > context" > [16:14] timbunce: Zefram: I think you'd have angry hordes after you. > [16:14] timbunce: better done in perlcritic > [16:14] PerlJam: timbunce: +1 > [16:14] mst: Zefram: but then Scalar::Defer won't work anymore > [16:14] Zefram: Scalar::Defer is an abomination > [16:15] mst: Zefram: an abomination that's heavily used in the > pumpking's production code > [16:16] timbunce: mst Zefram: I think Scalar::Defer could still work. > The pp_ref code just needs to know if it should return sv_yes or sv_no > > In boolean context, pp_ref would check the pv returned by sv_reftype > in > the same way that SvTRUE does (for "" and "0") and the push &sv_yes or > &sv_no. > Tim Bunce proposed this approach more than six years ago. Can anyone respond? Thank you very much. -- James E Keenan (jkeenan@cpan.org) --- via perlbug: queue: perl5 status: new https://rt.perl.org/Ticket/Display.html?id=78288Thread Next