mirror of
https://github.com/edwinb/Idris2-boot.git
synced 2024-12-18 18:31:43 +03:00
19 lines
465 B
Idris
19 lines
465 B
Idris
|
|
||
|
|
data Vect : Nat -> Type -> Type where
|
||
|
|
Nil : Vect Z a
|
||
|
|
(::) : a -> Vect k a -> Vect (S k) a
|
||
|
|
|
||
|
|
data Elem : a -> Vect n a -> Type where
|
||
|
|
Here : Elem x (x :: xs)
|
||
|
|
There : {xs : Vect n a} -> Elem x xs -> Elem x (y :: xs)
|
||
|
|
|
||
|
|
getIndex : Elem x xs -> Nat
|
||
|
|
getIndex Here = 0
|
||
|
|
getIndex (There p) = S (getIndex p)
|
||
|
|
|
||
|
|
Beatles : Vect ? String
|
||
|
|
Beatles = ["John", "Paul", "George", "Ringo"]
|
||
|
|
|
||
|
|
georgeInBeatles : Elem "George" Beatles
|
||
|
|
georgeInBeatles = There (There Here)
|