(* Copyright 2012-2015 by Adam Petcher.				* * Use of this source code is governed by the license described	* * in the LICENSE file at the root of the source tree.		*)
Set Implicit Arguments.
Local Open Scope list_scope.

(* Specifications: *)
Theorem removeFirst_In_length :
forall (A : Set)(eqd : EqDec A)(ls : list A)(a : A),
In a ls ->
length (removeFirst (EqDec_dec _ ) ls a) = pred (length ls).