lean2/tests/lean/hott/cases.hlean

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open nat
inductive vec (A : Type) : nat → Type :=
nil {} : vec A zero,
cons : Π {n}, A → vec A n → vec A (succ n)
namespace vec
variables {A B C : Type}
variables {n m : nat}
notation a :: b := cons a b
protected definition destruct (v : vec A (succ n)) {P : Π {n : nat}, vec A (succ n) → Type}
(H : Π {n : nat} (h : A) (t : vec A n), P (h :: t)) : P v :=
begin
cases v with (n', h', t'),
apply (H h' t')
end
end vec