Re^2: regex to capture an unsigned decimal value, but also preserve the user's formatting.

Hello davido,

Your use of the + (possessive) quantifier is ingenious, as it leads to simple, elegant code. I think you need to backslash the dot to avoid matching any character:

say "$_ => [", (m/(\d*\.?+\d*)/x ? "$1]" : ']');
#                     ^
[download]

But my main quibble is that this doesn’t work consistently if the decimal is embedded in a longer string. (Whether that’s actually a requirement isn’t clear from the OP.) For that, I came up with the following regex, which is verbose but seems to work OK:

#! perl
use strict;
use warnings;
use feature qw( say );

my $decimal = qr{
                    (
                        (?: \d+ \.? \d* ) |
                        (?: \d* \.? \d+ )
                    )
                }x;

while (<DATA>)
{
    chomp;
    next unless length;
    say "$_ => [", (/$decimal/x ? "$1]" : ']');
}

__DATA__
0.12
.12
12.
12
no numbers here
abc.def42
.7zx
[download]

Output:

16:39 >perl 1621_SoPW.pl
0.12 => [0.12]
.12 => [.12]
12. => [12.]
12 => [12]
no numbers here => []
abc.def42 => [42]
.7zx => [.7]

16:39 >
[download]

Cheers,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

Comment on Re^2: regex to capture an unsigned decimal value, but also preserve the user's formatting. Select or Download Code

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Re^3: regex to capture an unsigned decimal value, but also preserve the user's formatting. by davido (Cardinal) on May 04, 2016 at 15:00 UTC
Correct on both counts: (1) The dot should have been backslashed. (Edit: I've fixed the backslashing of `.`) (2) This works only for strings that don't contain dots anywhere to the left of the target "number". :). I didn't see any in his sample input, but the possibility supports the notion of "You have a problem. You think 'I will solve it with a regular expression.' Now you have two problems." A better solution would probably leverage Regexp::Common, or the regular expressions revealed in perlfaq4 under "How do I determine whether a scalar is a number/whole/integer/float?" Dave	[reply] [d/l]
Re^3: regex to capture an unsigned decimal value, but also preserve the user's formatting. by AnomalousMonk (Archbishop) on May 04, 2016 at 14:47 UTC
I think the other important point to make is that the order of the sub-patterns in the ordered alternation is critical: `c:\@Work\Perl\monks>perl -wMstrict -le "my $ufp = qr{ \d* [.]? \d+ \| \d+ [.]? \d* }xms; ;; for my $s (qw(0.12 .34 56. 78)) { printf qq{'$s' -> }; printf qq{'$1' \n} if $s =~ m{ ($ufp) }xms; } ;; my $s = '0.12 -0.98 .34 -.76 56. -54. 78 -32 bla bla abc.def42 .7zx'; printf qq{'$1' } while $s =~ m{ ($ufp) }xmsg; " '0.12' -> '0.12' '.34' -> '.34' '56.' -> '56' '78' -> '78' '0.12' '0.98' '.34' '.76' '56' '54' '78' '32' '42' '.7'` [download] (See `'56.'` and `'-54.'` instances.) Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]