RosettaCodeData/Task/Digital-root/Jq/digital-root-3.jq

$ jq -M -n -r -c -f Digital_root.jq

          i : [DR, P]
      961038: [9,2]
923594037444: [9,2]
      670033: [1,3]
448944221089: [1,3]

digital_root("1" * 100000) => [1,2]