Re^2: No garbage collection for my-variables

In addition to moritz's excellent point that a function that modifies its arguments then could not be called with a literal, I'd also point out that a lot of Perl programmers probably don't know that @_ is full of aliases. I'd been programming in Perl off and on for over ten years before I came to the Monastery and learned that @_ is aliases. I've asked about this feature in interviews I've conducted, and the prospects out there have always been surprised at this feature. Documentation helps, of course, but someone who doesn't know this is possible could spend an awful lot of time debugging before discovering this (as you say) action at a distance.

Thumbs up on the use less, however.

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Re^3: No garbage collection for my-variables by BrowserUk (Patriarch) on Sep 16, 2008 at 22:10 UTC
Done right, you can have both (see Re^3: No garbage collection for my-variables). That way, the unaware are not caught out, but when the facility is needed it is available. It's the same mechanism that sort uses for in-place sorting in 5.10. I've thought about patching List::Util`::shuffle()` in the same way. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l]
Re^4: No garbage collection for my-variables by ikegami (Patriarch) on Sep 17, 2008 at 03:10 UTC
`@a = sort @a` is done in place before 5.10 `>perl580\bin\perl -MO=Concise -e"@a = sort @a" 2>&1 \| find "sort" 7 <@> sort lK ->8 >perl588\bin\perl -MO=Concise -e"@a = sort @a" 2>&1 \| find "sort" 7 <@> sort lK/INPLACE ->8 >perl5100\bin\perl -MO=Concise -e"@a = sort @a" 2>&1 \| find "sort" 7 <@> sort lK/INPLACE ->8` [download] I don't have 5.8.1 to 5.8.7, so let's consult the perldeltas. perl584delta: In place sort optimised (eg `@a = sort @a`) But it was buggy in 5.8.4. perl585delta: The in-place sort optimisation introduced in 5.8.4 had a bug. For example, in code such as `@a = sort ($b, @a)`, the result would omit the value $b. This is now fixed.	[reply] [d/l] [select]
Re^4: No garbage collection for my-variables by betterworld (Curate) on Sep 16, 2008 at 22:35 UTC
It's the same mechanism that sort uses for in-place sorting in 5.10. I've thought about patching List::Util::shuffle() in the same way. I thought what you meant was that a subroutine can detect its being called in void context? But if I am not mistaken, 5.10's in-place sorting does not happen in void context: `% perl5.10.0 -lwe '@a = (2,1); sort @a; print @a' Useless use of sort in void context at -e line 1. 21` [download] As I understand it, perl (5.10) will detect that in `@a = sort @a`, the destination array is the same as the source array, so it uses a more efficient algorithm (but it's still in list context).	[reply] [d/l] [select]
Re^5: No garbage collection for my-variables by BrowserUk (Patriarch) on Sep 17, 2008 at 00:08 UTC
You're right. It is implemented that way. I should really get around to using these features, not just relying on half remembered discussion of what 5.10 can do. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply]
Re^3: No garbage collection for my-variables by shmem (Chancellor) on Sep 16, 2008 at 22:48 UTC
that a function that modifies its arguments then could not be called with a literal There are edge cases. See foreach funny business.	[reply]