Re^2: Question on SV internals

Yes, until you next use it in a string context.

There's no such terminating condition.

>perl -MDevel::Peek -e"$_ = '20 ducks'; Dump($_); 0+$_; Dump($_); ''.$
+_; Dump($_);"
...
SV = PVNV(0x163a454) at 0x342be4
  REFCNT = 1
  FLAGS = (POK,pIOK,pNOK,pPOK)
  IV = 20
  NV = 20
  PV = 0x1639b14 "20 ducks"\0
  CUR = 8
  LEN = 12
[download]

Another way to check is to count the number of numeric warnings:

>perl -wE"$_='20 ducks'; say 0+$_; say 0+$_; say ''.$_; say 0+$_;"
Argument "20 ducks" isn't numeric in addition (+) at -e line 1.
20
20
20 ducks
20
[download]

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Re^3: Question on SV internals by BrowserUk (Patriarch) on May 08, 2011 at 16:42 UTC
`$s = '20 ducks';; Dump $s;; SV = PV(0x18aec0) at 0xa5b48 REFCNT = 1 FLAGS = (POK,pPOK) PV = 0x40cad18 "20 ducks"\0 CUR = 8 LEN = 16` [download] Length = 16. Now use it in a numeric constant. `$s += 1;; Argument "20 ducks" isn't numeric in addition (+) at (eval 13) line 1, + <STDIN> line 4. Dump $s;; SV = PVNV(0x40b1eb8) at 0xa5b48 REFCNT = 1 FLAGS = (NOK,pNOK) IV = 20 NV = 21 PV = 0x40cad18 "20 ducks"\0 CUR = 8 LEN = 16` [download] Hm. Length still 16, but we gained an IV = 20 and an NV = 21; so we gained 12 or 16 bytes. Oh, and the PV no longer reflects the value of the scalar, so when you use it in a string context, a conversion has to happen! `print $s;; 21 Dump $s;; SV = PVNV(0x40b1eb8) at 0xa5b48 REFCNT = 1 FLAGS = (NOK,POK,pNOK,pPOK) IV = 20 NV = 21 PV = 0x40d3068 "21"\0 CUR = 2 LEN = 40` [download] Which modifies the PV and oops, it grew to 40 bytes in the process. And I don't care how you try to weasel out of it, the evidence is right there for those that care to look. So don't bother. 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.	[reply] [d/l] [select]
Re^4: Question on SV internals by ikegami (Patriarch) on May 08, 2011 at 16:47 UTC
Now use it in a numeric constant. $s += 1; `$s += 1` does more than "use it in a numeric context". Update: Furthermore, even though you went outside the scope of the question, the scalar still has a numerical value throughout. `FLAGS = (NOK,pNOK)` `FLAGS = (NOK,POK,pNOK,pPOK)` There is no such terminating condition.	[reply] [d/l] [select]
Re^5: Question on SV internals by BrowserUk (Patriarch) on May 08, 2011 at 19:09 UTC
does more than "use it in a numeric context". And of course, that could never happen in a real program. Take your blinkers off. 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.	[reply]
Re^6: Question on SV internals by ikegami (Patriarch) on May 08, 2011 at 23:53 UTC