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Re: Check for Positive Integer entry only

by swampyankee (Parson)
on May 09, 2007 at 18:08 UTC ( #614465=note: print w/replies, xml ) Need Help??

in reply to Check for Positive Integer entry only

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.


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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