Check number divisibility with regular expressions

Question

Given a decimal number N as a string of digits, how do I check if it\'s divisible by M using regular expressions only, without con

Answer 1

If your numbers are unary based, you can use this regex: s/1{divisor}//g then test if the number is empty.

Here is a Perl way to do it

my @divs = (2,3,5,7,11,13);
for my $num(2..26) {
    my $unary = '1'x$num; # convert num to unary
    print "\n$num can be divided by : ";
    for(@divs) {
        my $test = $unary;
        $test =~ s/1{$_}//g;
        print "$_, " unless $test;
    }
}

output:

2 can be divided by : 2, 
3 can be divided by : 3, 
4 can be divided by : 2, 
5 can be divided by : 5, 
6 can be divided by : 2, 3, 
7 can be divided by : 7, 
8 can be divided by : 2, 
9 can be divided by : 3, 
10 can be divided by : 2, 5, 
11 can be divided by : 11, 
12 can be divided by : 2, 3, 
13 can be divided by : 13, 
14 can be divided by : 2, 7, 
15 can be divided by : 3, 5, 
16 can be divided by : 2, 
17 can be divided by : 
18 can be divided by : 2, 3, 
19 can be divided by : 
20 can be divided by : 2, 5, 
21 can be divided by : 3, 7, 
22 can be divided by : 2, 11, 
23 can be divided by : 
24 can be divided by : 2, 3, 
25 can be divided by : 5, 
26 can be divided by : 2, 13,