Checking for data types

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hello I have really simple question, is there some function for checking the type of a scalar (string or number)?

I want to do something like:

my ($string, $salt) = @_;
$crc = 0xFFFFFFFF;
if (defined $salt) {
    if (isString $salt) {
        $string = $salt.$string;
    }
    elsif (isNumber $salt) {
        $crc = $salt;
    }
}
[download]

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Re: Checking for data types by samtregar (Abbot) on Sep 29, 2005 at 15:11 UTC
There are lots of ways to do this. Here's one which matches how Perl works internally when it needs to decide if something is numeric: `use Scalar::Util qw(looks_like_number); if (looks_like_number($foo)) { print "It could be a number.\n"; } else { print "It's just a string.\n"; }` [download] Other solutions could involve regexes from Regexp::Common or coded by hand. -sam	[reply] [d/l]
Re: Checking for data types by gryphon (Abbot) on Sep 29, 2005 at 15:10 UTC
Greetings, You could do a regex to check that there aren't any non-digit characters. Just replace your elsif conditional with this: `elsif ($salt !~ /\D/) {` [download] But looking at your example, do you want something a little bit more specific? Do you want only numbers in a particular range? gryphon Whitepages.com Development Manager (DSMS) code('Perl') \|\| die;	[reply] [d/l]
Re: Checking for data types by jZed (Prior) on Sep 29, 2005 at 15:40 UTC
As mentioned by others, you can construct a regex (though it needs to be somewhat complicated if you want to catch all formats of numbers rather than just digits and floats e.g. scientific notation). Scalar::Util::looks_like_number() is easier. If you happen to be using DBI in your script anyway, it has its own implementatin of looks_like_number() so you can use it rather than requiring Scalar::Util.	[reply]