optimize head/tail #70
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leonerd
reviewed
Nov 26, 2018
| XSRETURN( end - start ); | ||
| while (--size >= 0) { | ||
| ++SP; | ||
| *SP = *(SP + start); |
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Hmm.. This is quite the change of behaviour - we're now returning aliases of the original input list, rather than new temporary SVs that copy it. This would have a change of behaviour in lvalue context; for example
my @n = (1 .. 10);
$_++ for tail 4, @n;
I'm undecided if that's a good thing or not.
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If such code wouldn't work before, I'd say this would just be a new feature...
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It could be considered a feature yes. But it's a somewhat surprising change of behaviour. Is there a chance of accidental collateral damage?
I've asked for further opinion on p5p@ since it's a core module.
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Returning aliases is the behavior I would expect.
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Seeing e559254, I couldn't pass. This greatly speeds it up and cuts code to half from the original.