private static Zen <Option <ushort> > IndexOf(Zen <IList <ushort> > s, Zen <IList <ushort> > sub, int current)
{
return(s.Case(
empty: If(sub.IsEmpty(), Some <ushort>((ushort)current), Null <ushort>()),
cons: (hd, tl) => If(StartsWith(s, sub), Some <ushort>((ushort)current), IndexOf(tl, sub, current + 1))));
}
private static Zen <bool> Contains(Zen <IList <ushort> > s, Zen <IList <ushort> > sub)
{
return(s.Case(
empty: sub.IsEmpty(),
cons: (hd, tl) => OrIf(StartsWith(s, sub), Contains(tl, sub))));
}