Re^4: Changing array by changing $

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Re^5: Changing array by changing $_? by ikegami (Patriarch) on Oct 13, 2008 at 15:38 UTC
For lexicals, couldn't the check be done at compile-time?	[reply]
Re^6: Changing array by changing $_? by JavaFan (Canon) on Oct 13, 2008 at 17:02 UTC
`chomp (my $module = shift); require $module or die; for my $foo (@array) { func($foo); }` [download] How are you going to determine at compile time whether $foo gets modified? Because if `func` changes its `$_[0]`, the elements of `@array` get modified.	[reply] [d/l] [select]
Re^7: Changing array by changing $_? by ikegami (Patriarch) on Oct 13, 2008 at 17:17 UTC
I knew I phrased it as a question for a reason :D	[reply]
Re^7: Changing array by changing $_? by gone2015 (Deacon) on Oct 13, 2008 at 17:42 UTC
There's a mechanism to cope with: `func('Hello Sailor') ;` [download] which might be extended to passing of aliases, under suitable strictness... You are right. This particular trap is deeper, darker and altogether more ghastly than I thought !	[reply] [d/l]
Re^8: Changing array by changing $_? by ikegami (Patriarch) on Oct 13, 2008 at 18:56 UTC
Re^9: Changing array by changing $_? by gone2015 (Deacon) on Oct 13, 2008 at 22:07 UTC
Re^5: Changing array by changing $_? by gone2015 (Deacon) on Oct 13, 2008 at 16:10 UTC
OK. I can just about imagine how assignment to an ordinary scalar and assignment via an alias would be the same at run-time -- at run-time it doesn't much matter where the pointer to the SV has come from. However, I would have thought that the two must be distinguished at compile time -- something has to take care of the implied dereference -- for no run-time penalty. I realise that there are plenty of other traps for the new and the unwary -- but I can still remember the pain of learning about this one !	[reply]
Re^6: Changing array by changing $_? by ikegami (Patriarch) on Oct 13, 2008 at 16:23 UTC
I would have thought that the two must be distinguished at compile time A lexical var is either always an alias or never an alias, so you can for those. But it's a different story for globals. `sub func { $_ = "foo"; } func() for my $var; # $_ is an alias func(); # $_ isn't an alias` [download] Update: Oops, not even for lexicals if you use Data::Alias. But you could say that if `alias` is being used, you know you're dealing with an alias.	[reply] [d/l] [select]