mutual

inductive isEvenList : List α → Prop
| nil (α)  : isEvenList (α := α) []
| cons (h : α) {t : List α} : isOddList t → isEvenList (h::t)

inductive isOddList : List α → Prop
| cons (h : α) {t : List α} : isEvenList t → isOddList (h::t)
end
set_option pp.explicit true
#print isEvenList
#check @isEvenList.nil
#check @isEvenList.cons
#check @isOddList.cons
#check isEvenList.nil Nat
#check isEvenList.cons 1 $ isOddList.cons 2 $ isEvenList.nil Nat