Why does sv_2nv on non-number look like an NV

mje has asked for the wisdom of the Perl Monks concerning the following question:

I'm having a problem making a patch to a module work which contains the following code:

/* sv contains "aa" i.e., SvPOK(sv) is true and pv="aa"
sv_2nv(sv);
cast_ok = SvNOK(sv);
/* now cast_ok contains 512! */
/* and SvNV(sv) is 0 */
[download]

sv contains "aa" in pv and was created by $val = "aa". Printing SvPV_nolen confirms pv contains "aa". Since "aa" is not a valid double then why is SvNV true and why does SvNV return 0?

Comment on Why does sv_2nv on non-number look like an NV Download Code

Replies are listed 'Best First'.
Re: Why does sv_2nv on non-number look like an NV by Anonymous Monk on Nov 26, 2009 at 13:51 UTC
Because sv_2nv turns it into a double?	[reply]
Re^2: Why does sv_2nv on non-number look like an NV by mje (Curate) on Nov 26, 2009 at 14:02 UTC
How can you turn "aa" into a double?	[reply]
Re^3: Why does sv_2nv on non-number look like an NV by ikegami (Patriarch) on Nov 26, 2009 at 15:41 UTC
With difficulty. You get zero `>perl -e"print 0+'aa'" 0` [download]	[reply] [d/l]
Re^4: Why does sv_2nv on non-number look like an NV by mje (Curate) on Nov 26, 2009 at 15:48 UTC
Re^5: Why does sv_2nv on non-number look like an NV by almut (Canon) on Nov 26, 2009 at 16:00 UTC
Some notes below your chosen depth have not been shown here
Re^5: Why does sv_2nv on non-number look like an NV by ikegami (Patriarch) on Nov 26, 2009 at 16:08 UTC
Some notes below your chosen depth have not been shown here