vampire_numbers.sf

#!/usr/bin/ruby

#
## https://rosettacode.org/wiki/Vampire_number
#

func is_vampire (n) {
    return [] if n.ilog10.is_even

    var l1 = n.isqrt.ilog10.ipow10
    var l2 = n.isqrt

    var s = n.digits.sort.join

    gather {
        n.divisors.each { |d|

            d < l1 && next
            d > l2 && break

            var t = n/d

            next if (d%%10 && t%%10)
            next if ("#{d}#{t}".sort != s)

            take([d, t])
        }
    }
}

say "First 25 Vampire Numbers:"

with (1) { |i|
    for (var n = 1; i <= 25; ++n) {
        var fangs = is_vampire(n)
        printf("%2d. %6s : %s\n", i++, n, fangs.join(' ')) if fangs
    }
}

say "\nIndividual tests:"

[16758243290880, 24959017348650, 14593825548650].each { |n|
    var fangs = is_vampire(n)
    say "#{n}: #{fangs ? fangs.join(', ') : 'is not a vampire number'}"
}