product of digit of sum

As an exercise, I’ve been trying to write code that’s more “functional”. This was a nice one to practice some recursion!

Crystal:

def sum_dig_prod(*args)
  sum = args.sum
  sum_arr = sum.to_s.chars.map { |i| i.to_i }
  product = sum_arr.reduce { |a, b| a * b }
  return product if product.to_s.size == 1
  sum_dig_prod(product.to_i)
end

Nim:

func sumDigProd(args: varargs[int]): int =
    let sum = args.toSeq.foldl(a + b)
    let sumArr = ($sum).toSeq.mapIt(($it).parseInt) 
    let prod = sumArr.foldl(a * b)
    if ($prod).len == 1: return prod
    sumDigProd(prod)

Raku:

sub sum-dig-prod(*@args) {
    my $s = [+] @args;
    my @str-arr = $s.Str.comb;
    my $prod = [*] @str-arr;
    return $prod if $prod.Str.comb.elems == 1;
    sum-dig-prod($prod);
}

Raku really shines when it comes to problems like this - prefix operators keep the code short and concise.

Javascript:

function sumDigProd(...args: number[]) {
  const sum = args.reduce((acc, curr) => acc + curr);
  const arr = sum
    .toString()
    .split("")
    .map((i) => parseInt(i));
  const prod = arr.reduce((acc, curr) => acc * curr);
  if (prod.toString().length == 1) return prod;
  return sumDigProd(prod);
}