Digital root (recursive)

# Self-authored for the EML case corpus (no external origin). Repeatedly
# sums a number's digits, recursively, until a single digit remains (its
# "digital root") — a deliberate contrast with the corpus's existing
# examples/sum-of-digits-recursive/, which sums digits only once.

def sum_digits(n):
    if n < 10:
        return n
    return n % 10 + sum_digits(int(n / 10))

def digital_root(n):
    sum_digits(n) => total
    if total < 10:
        return total
    return digital_root(total)

numbers^+[12345, 999, 8, 0, 132189]

for n in numbers:
    digital_root(n) => root
    str(n) + " -> digital root " + str(root) => line
    line^0

def sum_digits(n):
    if n < 10:
        return n
    return n % 10 + sum_digits(int(n / 10))

def digital_root(n):
    total = sum_digits(n)
    if total < 10:
        return total
    return digital_root(total)

numbers = [12345, 999, 8, 0, 132189]
for n in numbers:
    root = digital_root(n)
    line = str(n) + " -> digital root " + str(root)
    print(line)

12345 -> digital root 6
999 -> digital root 9
8 -> digital root 8
0 -> digital root 0
132189 -> digital root 6

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