Rob Dixon schreef:
> Dr.Ruud:
>> Rob Dixon:
>>> A scalar cannot have multiple 'personalities' - it can have a
>>> maximum of two (its inherent type and a string equivalent) at any
>>> one time, but usually has only one.
>>
>> It can at least have 3: an integer numeric one, a floating numeric
>> one, and a string one. It can have more.
>
> No. It can be just a string; an integer and a string; a double and a
> string; or a reference (pointer) and a string. After that there's
> some weird stuff that goes on with tied scalars and so on. Basically
> every scalar data type keeps space for a pointer to its string
> equivalent as well, presumably because it's a useful thing to
> remember once it has been evaluated once.
1: all three of IOK and NOK and POK are set.
perl -Mstrict -Mwarnings -MData::Dumper -MDevel::Peek=Dump -wle'
my $s = "x";
defined($s) and do {
no warnings "numeric";
$s eq "" and 1;
$s == $_ and 1 for 0, 0.1;
};
print "\n", Dumper($s);
Dump $s;
'
$VAR1 = 'x';
SV = PVNV(0x8a19cb8) at 0x89bad2c
REFCNT = 1
FLAGS = (PADBUSY,PADMY,IOK,NOK,POK,pIOK,pNOK,pPOK)
IV = 0
NV = 0
PV = 0x89b6548 "x"\0
CUR = 1
LEN = 2
2: lossy, so no IOK.
perl -Mstrict -Mwarnings -MData::Dumper -MDevel::Peek=Dump -wle'
my $s = "122.99999999999999";
defined($s) and do {
no warnings "numeric";
$s eq "" and 1;
$s == $_ and 1 for 0, 0.1;
};
print "\n", Dumper($s);
Dump $s;
'
$VAR1 = '122.99999999999999';
SV = PVNV(0x88aba40) at 0x884cc3c
REFCNT = 1
FLAGS = (PADBUSY,PADMY,NOK,POK,pIOK,pNOK,pPOK)
IV = 122
NV = 123
PV = 0x8848700 "122.99999999999999"\0
CUR = 18
LEN = 19
3: a numeric string, touched by numeric comparisons, so returned as a
number by Dumper; again all of IOK, NOK and POK are set.
perl -Mstrict -Mwarnings -MData::Dumper -MDevel::Peek=Dump -wle'
my $s = "123";
$ARGV[0] and defined($s) and do {
no warnings "numeric";
$s eq "" and 1;
$s == $_ and 1 for 0, 0.1;
};
print "\n", Dumper($s);
Dump $s;
' 1
$VAR1 = 123;
SV = PVNV(0x8160dd0) at 0x8101be8
REFCNT = 1
FLAGS = (PADBUSY,PADMY,IOK,NOK,POK,pIOK,pNOK,pPOK)
IV = 123
NV = 123
PV = 0x80fd450 "123"\0
CUR = 3
LEN = 4
I would say that 1 and 3 have three personalities.
And 2 has nearly three. :)
4: make $s blessed too.
perl -Mstrict -Mwarnings -MData::Dumper -MDevel::Peek=Dump -wle'
my $s = "123";
bless \$s, "test";
defined($s) and do {
no warnings "numeric";
$s eq "" and 1;
$s == $_ and 1 for 0.1, 0;
};
print "\n", Dumper($s);
Dump $s;
'
$VAR1 = 123;
SV = PVMG(0x90f5618) at 0x9068c44
REFCNT = 1
FLAGS = (PADBUSY,PADMY,OBJECT,IOK,NOK,POK,pIOK,pNOK,pPOK)
IV = 123
NV = 123
PV = 0x9064460 "123"\0
CUR = 3
LEN = 4
STASH = 0x9063cf4 "test"
That last one is an example of what I named "more".
--
Affijn, Ruud
"Gewoon is een tijger."
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