Assigning anonymous hash to a list
Joseph Werner
telcodev at gmail.com
Tue Jul 30 21:33:33 BST 2013
I still disagree. This is a straightforward assignment to the first
element of a list.
In Perl, if you assign a scalar value to a list, the first variable in
the list will take that value, if it is assignable:
my ($i1, $i2, $i3) = 4;
say "\$i1 = ", $i1;
say "\$i2 = ", $i2;
say "\$i3 = ", $i3;
which gives:
$i1 = 4
Use of uninitialized value $i2 in say at test.pl line 11.
$i2 =
Use of uninitialized value $i3 in say at test.pl line 12.
$i3 =
Here I have assigned the scalar value 4 to the list element $i1, which
is assignable.
The comma operator is a valid component of a Perl expression.
my $str = 'text', {a => 1, b => 2, c => 3};
say $str;
which gives:
Useless use of anonymous hash ({}) in void context at test.pl line 5.
text
Again, this is a simple assignment of a scalar value to the first
element of a list, precedence is not involved.
Christian
On Tue, Jul 30, 2013 at 3:49 PM, Abigail <abigail at abigail.be> wrote:
> On Tue, Jul 30, 2013 at 03:34:48PM -0400, Joseph Werner wrote:
>> I disagree.
>>
>> This is a straightforward assignment to the first element of a list.
>> Precedence is not involved. A scalar assignment vs a list assignment
>> is the issue.
>>
>
>
> Thank you for playing.
>
>
> You are right it's straighforward, but you're wrong that it's scalar
> assignment vs list assignment.
>
> The fact there's "my ($str, $ref)" on the LHS of the assignment makes
> that Perl considers this a list assignment:
>
>
> $ perl -MO=Terse -e 'my ($str, $ref) = "text", {a => 1, b => 2, c => 3}'
> LISTOP (0x100324de0) leave [1]
> OP (0x100324e20) enter
> COP (0x100324d90) nextstate
> LISTOP (0x100301f10) list
> OP (0x100301ee0) pushmark
> BINOP (0x1003093c0) aassign [3]
> UNOP (0x100309950) null [148]
> OP (0x100309390) pushmark
> SVOP (0x100309d90) const PV (0x1008143c0) "text"
> UNOP (0x100329530) null [148]
> OP (0x100329570) pushmark
> OP (0x1003096e0) padsv [1]
> OP (0x100309600) padsv [2]
> LISTOP (0x100309460) anonhash
> OP (0x1003094a0) pushmark
> SVOP (0x100309400) const PV (0x100814408) "a"
> SVOP (0x100309430) const IV (0x1008143f0) 1
> SVOP (0x1003094d0) const PV (0x100814048) "b"
> SVOP (0x100309500) const IV (0x1008143a8) 2
> SVOP (0x100309530) const PV (0x100814378) "c"
> SVOP (0x100309560) const IV (0x100814390) 3
> -e syntax OK
> $
>
>
> Note the line: BINOP (0x1003093c0) aassign [3], and compare:
>
> $ perl -MO=Terse -e 'my ($str, $ref) = ("text", {a => 1, b => 2, c => 3})'
> LISTOP (0x100324d90) leave [1]
> OP (0x100324dd0) enter
> COP (0x100324d40) nextstate
> BINOP (0x100309570) aassign [3]
> UNOP (0x100301f10) null [148]
> OP (0x100301ee0) pushmark
> SVOP (0x100309d90) const PV (0x1008143c0) "text"
> LISTOP (0x1003093c0) anonhash
> OP (0x100309400) pushmark
> SVOP (0x100309950) const PV (0x100814450) "a"
> SVOP (0x100309390) const IV (0x100814408) 1
> SVOP (0x100309430) const PV (0x1008143f0) "b"
> SVOP (0x100309460) const IV (0x100814048) 2
> SVOP (0x100309490) const PV (0x1008143a8) "c"
> SVOP (0x1003094c0) const IV (0x100814378) 3
> UNOP (0x100329530) null [148]
> OP (0x100329570) pushmark
> OP (0x1003096e0) padsv [1]
> OP (0x100309600) padsv [2]
> -e syntax OK
> $
>
>
>
> Abigail
--
Best Regards,
[Joseph] Christian Werner Sr
C 360.920.7183
H 757.304.0502
Txt 757.304.0502
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