Re: Regexp for range of numbers

TIMTOWTDI, and I wanted to play with (?(condition)true-pattern|false-pattern) asserts.
Looks like this:

my $re =qr/
^(\d{1,3})$                             # Up to 3 digits
(?(?{ ($1<256 and $1>=0) })     # If in the correct range
                .?                      # An allways match
        |                       # Else
                .                       # Never going to match after e
+nd of string
)
/x;
[download]

Comment on Re: Regexp for range of numbers Select or Download Code

Replies are listed 'Best First'.
Re^2: Regexp for range of numbers by Roy Johnson (Monsignor) on Apr 05, 2005 at 12:16 UTC
You don't need to test against zero. Or put anything in the success-pattern; an empty pattern matches just fine. `/^(\d{1,3})$(?(?{$1<256 }) \| . )/x` [download] or you could move your anchor and use an impossible anchor for the fail-pattern: `/^(\d{1,3})(?(?{$1<256 }) $ \| ^ )/x` [download] Caution: Contents may have been coded under pressure.	[reply] [d/l] [select]
Re^3: Regexp for range of numbers by Anonymous Monk on Apr 05, 2005 at 12:37 UTC
I tend to use `(?!)` for the always fail pattern (there are no positions that aren't followed by the empty string). `^` might match if a `/m` flag is in use, or if the zero-width assertion is done at the beginning of the string. An empty string works fine as an always match pattern - or `(?=)` if you want to go symmetric.	[reply] [d/l] [select]