Regex and leading zeros in numbers

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

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Re: Regex and leading zeros in numbers by Roy Johnson (Monsignor) on Mar 24, 2004 at 16:23 UTC
Have you tried numeric comparison? Is that what you want? `my ($s1, $s2) = qw(20055 020055); print(($s1 == $s2) ? "equal\n" : "not equal\n");` [download] If you want to strip leading zeroes: `s/^0*//;` [download] The PerlMonk `tr///` Advocate	[reply] [d/l] [select]
Re: Regex and leading zeros in numbers by Happy-the-monk (Canon) on Mar 24, 2004 at 16:25 UTC
You did not tell us what the files look like. Anyway: Extract a series of digits: `m/(\d+)/` Extract a series of digits, throw away leading "0": `m/0(\d+)/` You can compare numbers numerically with the == operator, so you do not need to care about leading zeros.	[reply]
Re: Regex and leading zeros in numbers by flyingmoose (Priest) on Mar 24, 2004 at 17:42 UTC
Regarding the `(\d)(\d)` repitition you are using, I highly recommend you pick up a copy of "Learning Perl" and "Programming Perl" -- the O'Reilly Camel and Lllama books, as these explain regexes, and the fact tht you can do things like `(\d{0..9})` or `(\d*)` to specifiy a certain number of digits. It always helps to read a little documentation before charging too deeply into new things! :) While the 'don't use regexes' comments are 100% right, a regex cleanup solution could look something like `$x=~s/[0]?(\d+)/$1/;`. The question mark means 'optional', and the '+' means 'one or more of'. The $1 represents what you matched inside parens between the first set of slashes. So we are replacing digits with a leading zero with just the digits. Again, read the docs, they are excellent. (as usual, all code is untested)	[reply] [d/l] [select]
Re: Regex and leading zeros in numbers by QM (Parson) on Mar 24, 2004 at 18:42 UTC
If the numeric suggestions above don't solve your problem, read on... Matching usually involves the `m//` operator, while substitution usually involves the `s///` operator. While it is often useful and efficient to use the `s///` operator in an `if{}` statement, when starting out you might go a little slower. Assuming you have 2 variables, and you want to match the one (without leading zeros) to the other (with leading zeros), you might be looking for this: `$var1 = '020055'; $var2 = '20055'; if ( $var1 =~ /(0*)($var2)/ ) { print "Found match: <$1><$2>\n"; } else { print "No match: \$var1<$var1> \$var2<$var2>\n"; }` [download] which yields: `Found match: <0><20055>` [download] To be more helpful, we need to know more about your problem. For instance, are you reading each value from different files? Do the values have exactly 5 interesting digits? -QM -- Quantum Mechanics: The dreams stuff is made of	[reply] [d/l] [select]
Re: Regex and leading zeros in numbers by swkronenfeld (Hermit) on Mar 24, 2004 at 16:25 UTC
do you mean that you're trying to check if any two given generic numbers are equivalent, except that one of them has a leading zero? or are you specifically looking for those two numbers (20055 and 020055)?	[reply]