Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Pass hash as reference in Perl
Answer:
In the previous post, we talked about how to Pass hash as list in Perl, now we discuss another way: To pass a hash as a reference in Perl function.
sub foo {
my ($h) = @_;
print $h->{"1"};
}
foo ( {"1" => "One", "2" => "Two"} );
One will be printed out.
Pass hash as list in Perl
Answer:
To pass a hash as a list in Perl function, use the following way:
use strict;
use warnings;
sub foo {
my %h = @_;
print $h{1};
}
foo ( 1 => "One", 2 => "Two" );
One will be printed out.
Force Perl to use integer arithmetic
Answer:
To force Perl to use integer arithmetic, instead of floating point, you just need to add the statement "use integer;" at the beginning of your script.
Example:
use strict;
use warnings;
use integer;
my $i = 10/3;
print $i;
It above program will print out 3 instead of 3.333..
Return the last evaluated statement from function in Perl
Answer:
By default, Perl does not require you to explicit return the the last evaluated statement from function.
E.g.
print function1();
sub function1 {
my $i = 99;
}
The above program will output 99, and you can see the return statement is not needed and it is a valid Perl program.
Is Perl pass by reference or pass by value?
Answer:
(Edit: Thanks Matt for the feedback, I have updated the answer.)
It depends on how your function is implemented
See the code below:
package Dog;
sub new {
my ($class, $name) = @_;
my $self = { "name" => $name };
bless $self, $class;
return $self;
}
// Pass by value
sub Foo {
my $d = shift;
$d = new Dog("Another");
}
// Pass by reference
sub Bar {
$_[0] = new Dog("Another");
}
my $d = new Dog("Peter");
Foo($d); // Pass by value, $d not changed, so it print out "Peter"
print $d->{"name"};
Bar($d); // Pass by reference, $d is changed, so it print out "Another"
print $d->{"name"};
