3c11cca3cb
This PR upstreams lemmas about List/Array operations already defined in Lean from std/batteries. Happy to take suggestions about increasing or decreasing scope. --------- Co-authored-by: Mario Carneiro <di.gama@gmail.com>
16 lines
422 B
Text
16 lines
422 B
Text
namespace List
|
||
|
||
@[simp] theorem filter_append' {as bs : List α} {p : α → Bool} :
|
||
filter p (as ++ bs) = filter p as ++ filter p bs :=
|
||
match as with
|
||
| [] => by simp
|
||
| a :: as => by
|
||
rw [filter_cons, cons_append, filter_cons]
|
||
cases p a
|
||
simp [filter_append]
|
||
simp [filter_append]
|
||
|
||
-- the previous contains a more complicated version of
|
||
def f : Nat → Nat
|
||
| 0 => 1
|
||
| i+1 => (fun x => f x) i
|