I think that this exact case is handled in the Camel Book.
The logic is quite straightforward:
#!perl
use strict;
use warnings;
while (<DATA>) {
chomp; # get rid of pesky newlines
if(is_integer_string($_)){
print "$_ is a valid integer string\n";
}
else {
print "$_ isn't a valid integer string\n";
}
}
sub is_integer_string {
# a valid integer is any amount of white space, followed
# by an optional sign, followed by at least one digit,
# followed by any amount of white space
return $_[0] =~ /^\s*[\+\-]?\d+\s*$/;
}
__DATA__
1
1234
+1234
-1234
A
1234+
+ 1234
Note that this does not check to see if the integer can be represented on your system. It also does not permit white space between the sign and the leading digit of the number being examined.
Oops! This will pass 0, which is not a positive integer, although it is a valid integer.
To correct the test replace this:
return $_[0] =~ /^\s*[\+\-]?\d+\s*$/;
with this
if(( $_[0] =~ /^\s*[\+\-]?\d+\s*$/) and ($_[0] > 0)) {
return 1;
}
else{
return undef;
}
Doubtless, this is not the most efficient method.
emc
Insisting on perfect safety is for people who don't have the balls to live in the real world.
—Mary Shafer, NASA Dryden Flight Research Center
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