Re^8: Snarky comments on the ddj perl quiz (hijack, pvnv memory)

Our thread, for us to use and abuse as any of us see fit.

Did you know that:

  $x = "1.1"; $y = 0+$x;
[download]

leaves $x taking less memory than

  $x = 1.1; $y = "$x";
[download]

Comment on Re^8: Snarky comments on the ddj perl quiz (hijack, pvnv memory) Select or Download Code

Replies are listed 'Best First'.
(OT) Re^9: Snarky comments on the ddj perl quiz (hijack, pvnv memory) by Argel (Prior) on Aug 30, 2007 at 23:08 UTC
LOL!! No I didn't and asking why is certainly worthier than some of those DDJ questions! Okay, so I'll bite -- why does it use less? I really do not know enough about perl to answer that one and my C is getting very rusty. Still, I doubt a three element char* uses more memory than a float so this sounds like a Perl-ism. Does perl end up storing a numerical and a string version in the second example while just converting from a string to a numeric in the first example? Or put differently, does the first example give perl a better hint? Is this part of the Perl spec or just a side effect of the perl implementation?	[reply]
Re^10: Snarky comments on the ddj perl quiz (hijack, pvnv memory) by ysth (Canon) on Aug 31, 2007 at 02:08 UTC
Both store both the integer and character value. But one uses a 4-byte string buffer and one (for reasons unknown to me, but perhaps related to the longest conceivable stringification of a floating point number) uses a 36-byte string buffer.	[reply]
Re^11: Snarky comments on the ddj perl quiz (hijack, pvnv memory) by Argel (Prior) on Aug 31, 2007 at 15:52 UTC
Ahh, I see. In the first example the length is known because "1.1" is a constant so storing it can be optimized while in the second example "$x" to evaluated at runtime.	[reply]