euler3.opa

NUMBER = 600851475143
 
iter numbers = Iter.init(2, function(int elm){ elm + 1 }, function(int elm){ elm > 0 })
 
function iter remove_multiples(int a, iter seq){
    Iter.filter(function(int elm){ mod(elm, a) != 0 }, seq)
}
 
function primes_init(iter seq){
    match(seq.next()){
 
      case {none} : {  next : function () { none } }
      case {some:it} : { next : function () { some((it.f1, primes_init(remove_multiples(it.f1, it.f2)))) } }
 
    }
}
 
iter primes = primes_init(numbers)

function largest_factor(int n, iter ps){
    match(ps.next()){
 
      case {none} : { none }
      case {some:p} : { 
                        if(p.f1==n) some(p.f1)
                        else match(mod(n, p.f1)){
                            case 0 : largest_factor(n/p.f1, ps)
                            default : largest_factor(n , p.f2)
                        }
                      }
    }

}

option number = largest_factor(NUMBER,primes)

jlog(Int.to_string(Option.get(number)))