We don't bite newbies here... much PerlMonks

### Re: map a list - segfault

by imp (Priest)
 on Mar 12, 2007 at 20:00 UTC ( #604422=note: print w/replies, xml ) Need Help??

in reply to map a list

The block that caused the segfault doesn't work the way you think it does, because of precedence:
```perl -MO=Deparse -e '
(@n=(1,2) && (\$n[1],\$n[0]));
(@n=(1,2) && (\$n[1],\$n[0]));
(@n=(1,2) && (\$n[1],\$n[0]));
'
@n = ('???', 2) && (\$n[1], \$n[0]);
@n = ('???', 2) && (\$n[1], \$n[0]);
@n = ('???', 2) && (\$n[1], \$n[0]);
Using 'and' instead of && would work, or an extra set of parens.
```perl -MO=Deparse -e '
(@n=(1,2) && (\$n[1],\$n[0]));
((@n=(1,2)) && (\$n[1],\$n[0]));
(@n=(1,2) and (\$n[1],\$n[0]));
'
@n = ('???', 2) && (\$n[1], \$n[0]);
\$n[1], \$n[0] if @n = (1, 2);
\$n[1], \$n[0] if @n = (1, 2);

As for the segfault itself, I don't grok why it breaks but Devel::Peek gives a hint:

```perl -MDevel::Peek -le '
(@n=(1,2) && (\$n[1],\$n[0])); print Dump \@n;
(@n=(1,2) && (\$n[1],\$n[0])); print Dump \@n;'
SV = RV(0x3c02b018) at 0x3c0062dc
REFCNT = 1
FLAGS = (TEMP,ROK)
RV = 0x3c011718
SV = PVAV(0x3c0084dc) at 0x3c011718
REFCNT = 2
FLAGS = ()
IV = 0
NV = 0
ARRAY = 0x3c02a4f0
FILL = 1
MAX = 3
ARYLEN = 0x0
FLAGS = (REAL)
Elt No. 0
SV = NULL(0x0) at 0x3c006168
REFCNT = 1
FLAGS = ()
Elt No. 1
SV = NULL(0x0) at 0x3c006264
REFCNT = 1
FLAGS = ()

SV = RV(0x3c02b018) at 0x3c0062dc
REFCNT = 1
FLAGS = (TEMP,ROK)
RV = 0x3c011718
SV = PVAV(0x3c0084dc) at 0x3c011718
REFCNT = 2
FLAGS = ()
IV = 0
NV = 0
ARRAY = 0x3c02a4f0
FILL = 1
MAX = 3
ARYLEN = 0x0
FLAGS = (REAL)
Elt No. 0
SV = UNKNOWN(0xff) (0x0) at 0x3c006168
REFCNT = 1
FLAGS = ()
Elt No. 1
SV = UNKNOWN(0xff) (0x0) at 0x3c006264
REFCNT = 1
FLAGS = ()
Note that the array entries changed from :
```SV = NULL(0x0) at 0x3c006168
To:
```SV = UNKNOWN(0xff) (0x0) at 0x3c006168

Create A New User
Node Status?
node history
Node Type: note [id://604422]
help
Chatterbox?
and all is quiet...

How do I use this? | Other CB clients
Other Users?
Others contemplating the Monastery: (5)
As of 2018-03-23 04:34 GMT
Sections?
Information?
Find Nodes?
Leftovers?
Voting Booth?
When I think of a mole I think of:

Results (288 votes). Check out past polls.

Notices?