Theorem: Schema.length_nths (Table/SchemaFunctions.lean)

State before:
η : Type u_η
dec_η : DecidableEq η
schema : Schema
α : Type u_1
xs : List α
ns : List (Fin (length xs))
⊢ List.length (nths xs ns) = List.length ns
Tactic:
rw [nths, Schema.map_eq_List_map]
State after:
η : Type u_η
dec_η : DecidableEq η
schema : Schema
α : Type u_1
xs : List α
ns : List (Fin (length xs))
⊢ List.length (List.map (fun n => nth xs n.val (_ : n.val < length xs)) ns) = List.length ns

State before:
η : Type u_η
dec_η : DecidableEq η
schema : Schema
α : Type u_1
xs : List α
ns : List (Fin (length xs))
⊢ List.length (List.map (fun n => nth xs n.val (_ : n.val < length xs)) ns) = List.length ns
Tactic:
apply List.length_map
State after:
no goals