def osa_rows
import cli@0.2.0.0/cli.bend as Cliimport Base
5708def osa_rows(s: String, ap: Maybe<&2, Char>, +i: Nat, +b: String,
5709 +prev: List<&2, Nat>, prev2: List<&2, Nat>) -> List<&2, Nat>:
5710 match s:
5711 case SNil{}: prev
5712 case SCon{+a, tail}:
5713 osa_rows(tail, Some{a}, (i + 1n : Nat), b,
5714 i <> osa_row(b, None{}, a, ap, prev, 0n <> prev2, i), prev)