Question on pattern matching

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

Problem with pattern matching

Need in -if- statement that will detect when a 2 char string contains a non digit.( I’ve already checked the string's lenght so it's guaranteed to be 2 chars long.) In other words. The string can contain "00","01"."02"…"99" but NOT stuff like " 0". "0 ", "9A", "Z7"...

if ($my_dat =~ /^[0-9]/ ) {some code here;}
[download]

Works if the 1st char is not a digit ( catches stuff like " 0" and "A4" ) but misses stuff if 2nd char is not a digit ( Misses stuff like "0 " and "7W")

Can someone help ?

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Re: Question on pattern matching by Limbic~Region (Chancellor) on Jun 16, 2005 at 19:41 UTC
Joe_Cullity, If you already know that the string is two characters you can just say `if $str =~ /\D/ { print "non-digit" }` [download] If you want to kill two birds with one stone, you can verify length and digitness in one statement: `if $str !~ /^\d\d$/ { print "wrong length or contains non-digits" }` [download] Cheers - L~R	[reply] [d/l] [select]
Re: Question on pattern matching by Zaxo (Archbishop) on Jun 16, 2005 at 19:43 UTC
To test if the string is exactly two digits, anchor beginning and end and use a quantifier, `if ($my_dat !~ /^\d{2}$/) { # some code here }` [download] The !~ op negates the match so that the bracketed code is executed if $my_dat is different from two digits. After Compline, Zaxo	[reply] [d/l]
Re: Question on pattern matching by ikegami (Patriarch) on Jun 16, 2005 at 19:40 UTC
Check for a non-digit: `if ($my_dat =~ /[^0-9]/) { # $my_dat contains a non-digit. ... }` [download] or check for all digits: `if ($my_dat =~ /^[0-9]+$/) { # $my_dat only contains digits. ... }` [download] Update: If you need to make sure the string is only two characters long: `if ($my_dat =~ /^[0-9]{2}$/) { # $my_dat only contains digits. # $my_dat is exactly two characters long. ... }` [download]	[reply] [d/l] [select]
Re^2: Question on pattern matching by ikegami (Patriarch) on Jun 16, 2005 at 21:05 UTC
This also works: `if ($my_dat eq sprintf('%02d', do { no warnings; 0+$my_dat })) { # $my_dat only contains digits. # $my_dat is exactly two characters long. ... }` [download]	[reply] [d/l]
Re: Question on pattern matching by Transient (Hermit) on Jun 16, 2005 at 19:42 UTC
you want `if ( $my_dat =~ /[^0-9]/ ) { # code here to handle the non-digits` [download] your regexp looks for the beginning of the line followed by a digit... the one above looks for anything anywhere that is a NON-digit.	[reply] [d/l]
Re^2: Question on pattern matching by nobull (Friar) on Jun 16, 2005 at 20:42 UTC
`/[^0-9]/` is more concisely written `/\D/`.	[reply] [d/l] [select]
Re: Question on pattern matching by shady (Sexton) on Jun 16, 2005 at 22:00 UTC
If you want get match only in digits, to solve your problem write so: if ($my_dat =~ /^0-9$/ ) {some code here;} or if ($my_dat =~ /^\d+$/ ) {some code here;}	[reply]
Re: Question on pattern matching by sh1tn (Priest) on Jun 16, 2005 at 22:06 UTC
If the string is only two digits, you can use faster check with hash keys existence: `my %digits = map{ '0'x(2-length($_)).$_, 1 }0..99; #now keys in %digits are from 00,01 ... to 99 if( exists $digits{$my_dat} ){ ... }` [download]	[reply] [d/l]