On Wed, Sep 23, 2009 at 19:16, Mike McClain <mike.j...@nethere.com> wrote:
> On Tue, Sep 22, 2009 at 05:09:26AM -0400, Shawn H Corey wrote:
>> Roman Makurin wrote:
>> >Hi All!
>> >
>> >right now im doing it in following way:
>> >$size = @{[func_that_return_list_value]};
>> >
>> >is there any best way to do it ?
>> >
>> See `perldoc -f scalar` http://perldoc.perl.org/functions/scalar.html
>
> I read the perldoc on scaler and then tried every combination
> I could think of:
>
> perl -le ' sub farr{ return qw( k l m ); }
> $a = @{[farr]};
> $b = scalar farr;
> $c = scalar (farr);
> $d = scalar [farr];
> $e = scalar @{farr};
> $f = scalar @{[farr]};
> $g = () = farr;
> print "\n\$a = $a, \$b = $b, \$c = $c, \$d = $d, \$e = $e, \$f = $f, \$g =
> $g";'
>
> $a = 3, $b = m, $c = m, $d = ARRAY(0x814f8e4), $e = 0, $f = 3, $g = 3
>
> Unless there is a syntax I've missed, only a, f & g give the desired answer.
> To my thinking a is clearly preferable to f but the winner has to be g.
> =()= is much more legible than @{[]}, less prone to mistyping.
>
> Thank you Paul Johnson for bringing this to my attention.
>
> The original question was what's 'best'.
> Does anyone know of a case where one of these expressions would fail?
snip
Both the a and g cases only work because the assignment provides
scalar context. Failure to recognize this may cause you to write
my %h = (
a => @{[farr]},
g => () = farr,
);
which results in either an error (if farr returns an even number), or
worse, a very odd hash:
my %h = (
'a' => 'k',
'l' => 'm',
'g' => undef
);
The solution is to force scalar context with scalar:
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
sub farr { return qw/k l m/ }
my %h = (
a => scalar @{[farr]},
g => scalar(() = farr),
);
print Dumper \%h;
Of course, the best solution is to make farr context aware with the
poorly named [wantarray][1]:
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
sub farr {
my @a = qw/k l m/;
return wantarray ? @a : scalar @a;
}
my @list = farr;
my $count = farr;
print "[...@list] has $count items\n";
my %h = (
h => scalar farr,
);
print Dumper \%h;
[1] : http://perldoc.perl.org/functions/wantarray.html
--
Chas. Owens
wonkden.net
The most important skill a programmer can have is the ability to read.
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