how do i test a number negative or positive?


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how do i test a number negative or positive?

by dswimboy (Initiate)

on Apr 09, 2002 at 21:33 UTC ( #157866=categorized question: print w/replies, xml )

Need Help??

Contributed by dswimboy on Apr 09, 2002 at 21:33 UTC
Q&A > numbers

Description:

foreach $name (@excer) {
    if ($1 / 2) {
        print '<FONT color="Yellow" face="Times New Roman">',
              $name,
              '</FONT><BR>';
    } else {
        print '<FONT color="#ccffff" face="Times New Roman">',
              $name,
              '</FONT><BR>';
    }
    $i++;
}
[download]

That might help a little with showing you what i wanna do...alternate between font colors. if you know a better way, please inform me :)

Edited by davido: Reformatted code section, even though it has nothing to do with the actual question of "How do I test if a number is negative or positive."

Answer: how do i test a number negative or positive?
contributed by Kanji

For your original question, comparing with the abs value should do the trick ...

if ( $num == abs($num) ) {
    print "positive";
} else {
    print "negative";
}
[download]

... but for your revised question, you should check the modulus ...

if ( $num % 2 ) {
    print "odd";
} else {
    print "even";
}
[download]

However, if all you really want to do is alternate colours...

Edit by dws per author's request

Answer: how do i test a number negative or positive?
contributed by PodMaster

check out perlsyn and perlop (in particular the comparison operators)

my $num = $_ = 4;
if($num >= 0) {
   die "$num is positive";
} else {
   die "$num is negative (but we already knew that)";
}

# or even ;)
my $num = $_ = -4;
if(substr($num,0,1,) eq '-') {
   die "I, $num, feel so negative today";
} else {
   die "$num says 'Things are looking up'";
}

[download]

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