10 lines
264 B
Text
10 lines
264 B
Text
import data.nat
|
|
open nat
|
|
|
|
inductive List (T : Type) : Type :=
|
|
| nil {} : List T
|
|
| cons : T → List T → List T
|
|
|
|
definition length {T : Type} : List T → nat := List.rec 0 (fun x l m, succ m)
|
|
theorem length_nil {T : Type} : length (@List.nil T) = 0
|
|
:= eq.refl _
|