testing for array or scalar in a hash.

[Fred S]

Hi,
I have a hash containing, data, everything is generated on the fly so
my hash, has some scalars, and some arrays, in it.
How can I test wether a value of the hash is an array and then loop
through it ?
i did the following loop:
it will print the arrays but will skip the scalars,

foreach (keys %Options){
print $_." => \n";
foreach my $val (@{$Options{$_}}){
print "\t".$val;
print "\n";
}
}

Thanx for the help.


Fred

 

[Gunnar Hjalmarsson]

I have a hash containing, data, everything is generated on the fly
so my hash, has some scalars, and some arrays, in it.
How can I test wether a value of the hash is an array and then loop
through it ?

How about:

foreach (keys %Options){
if (ref $Options{$_} eq 'ARRAY') {
print ...

 

[Greg Bacon]

: I have a hash containing, data, everything is generated on the fly so
: my hash, has some scalars, and some arrays, in it.
: How can I test wether a value of the hash is an array and then loop
: through it ?
: [snip code]

Use Perl's ref operator to see whether you have an array reference:

#! /usr/local/bin/perl

use warnings;
use strict;

my %Options = (
scalar => 42,
arrayref => [ qw/ apples oranges bananas / ],
);

for (keys %Options) {
print $_, " => \n",
map "\t$_\n",
ref $Options{$_} ? @{ $Options{$_} } : $Options{$_};
}

This generates the following output:

scalar =>
42
arrayref =>
apples
oranges
bananas

You could pare the line lengths by iterating with the each operator.

Hope this helps,
Greg

 

[John W. Krahn]

I have a hash containing, data, everything is generated on the fly so
my hash, has some scalars, and some arrays, in it.
How can I test wether a value of the hash is an array and then loop
through it ?
i did the following loop:
it will print the arrays but will skip the scalars,

foreach (keys %Options){
print $_." => \n";
foreach my $val (@{$Options{$_}}){
print "\t".$val;
print "\n";
}
}

Use the ref operator.

for ( keys %Options ) {
print $_." => \n";
if ( ref eq 'ARRAY' ) {
print "\t", join( "\t", @{$Options{$_}} ), "\n";
}
}


perldoc -f ref


John

 

[David K. Wall]

I have a hash containing, data, everything is generated on the fly
so my hash, has some scalars, and some arrays, in it.
How can I test wether a value of the hash is an array and then
loop through it ?

perldoc -f ref

Example:

use strict;
use warnings;

my %h = (
a => [1,2,3,4],
h => {a=>1,b=>2,c=>3},
s => 'string'
);

foreach my $k (sort keys %h) {
print "$k -> ", ref $h{$k}, "\n";
}

Note that the output for $h{s} is blank, because $h{s} is a scalar,
not a reference to a scalar.

 

[Bart Lateur]

I have a hash containing, data, everything is generated on the fly so
my hash, has some scalars, and some arrays, in it.
How can I test wether a value of the hash is an array and then loop
through it ?

If *all* you have in there are array (refs) and scalars, then you can
use ref() as a boolean test. For scalars, it will return the empty
string (false), for array refs, "ARRAY" (true).