Perl code to differentiate numeric and non-numeric input

Raynon · #1 (**permalink**) 03-02-2007

Hi All,

Is there any code in Perl which can differentiate between numeric and non-numeric input?

cbkihong · #2 (**permalink**) 03-03-2007

The most common way:
Use regular expression.

Alternative (probably a better) way:

Code:

cbkihong@cbkihong:~$ perl -MScalar::Util -e 
'print(Scalar::Util::looks_like_number("-8.90e10")?"Looks like a number.\n":"Not a number.\n")'
Looks like a number.
cbkihong@cbkihong:~$ perl -MScalar::Util -e 
'print(Scalar::Util::looks_like_number("89d")?"Looks like a number.\n":"Not a number.\n")'
Not a number.

Raynon · #3 (**permalink**) 03-05-2007

Hi ,

Below is my Perl code using regular expression. but it doesn;t seem to work.
Can anybody tell me what's wrong with my code ?

Code:

#!/usr/bin/perl

print "Enter a term: ";
$Input = <STDIN>;
print "\n";

if ($input == [0-9]) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}

anbu23 · #4 (**permalink**) 03-05-2007

Code:

#!/usr/bin/perl

print "Enter a term: ";
$input = <STDIN>;
print "\n";

if ($input =~ /^[0-9]+$/) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}

Yogesh Sawant · #5 (**permalink**) 03-05-2007

Quote:

Originally Posted by anbu23

Code:

#!/usr/bin/perl

print "Enter a term: ";
$input = <STDIN>;
print "\n";

if ($input =~ /^[0-9]+$/) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}

i don't intend to flame you, but wish to point out a few deficiencies in your code - it doesn't consider negative numbers, and real numbers, in current form, it is identifying natural numbers, along with zero

Yogesh Sawant · #6 (**permalink**) 03-05-2007

this one identifies integers, real numbers, and negative numbers as well:

Code:

#!/usr/bin/perl
use strict;

print "Enter a number: ";
chomp (my $num = <STDIN>);

if ($num =~ m/^-?\d+$/) {
    print "An integer \n";
}
elsif ($num =~ m/^-?\d+[\/|\.]\d+$/) {
    print "real number! \n";
}
else {
    print "not a number \n";
}

anbu23 · #7 (**permalink**) 03-05-2007

Quote:

Originally Posted by Yogesh Sawant

i don't intend to flame you, but wish to point out a few deficiencies in your code - it doesn't consider negative numbers, and real numbers, in current form, it is identifying natural numbers, along with zero

Code:

#!/usr/bin/perl

print "Enter a term: ";
$input = <STDIN>;
print "\n";

if ( $input =~ /^[\+-]*[0-9]*\.*[0-9]*$/ && $input !~ /^[\. ]*$/  ) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}

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