my first coq

形式化方法作业

写下第一题

一个好的开始

 

(** **** Exercise: 1 star (nandb) *)
(** Complete the definition of the following function, then make
    sure that the [Example] assertions below each can be verified by
    Coq.  *)

(** This function should return [true] if either or both of
    its inputs are [false]. *)

Definition nandb (b1:bool) (b2:bool) : bool :=
  (* FILL IN HERE *)
  match b1 with
  | true => (negb b2)
  | false => true
  end.

(** Remove "[Admitted.]" and fill in each proof with
    "[Proof. simpl. reflexivity. Qed.]" *)

Example test_nandb1:               (nandb true false) = true.
Proof. simpl. reflexivity. Qed.
 
Example test_nandb2:               (nandb false false) = true.
Proof. simpl. reflexivity. Qed.
 
Example test_nandb3:               (nandb false true) = true.
Proof. simpl. reflexivity. Qed.
 
Example test_nandb4:               (nandb true true) = false.
Proof. simpl. reflexivity. Qed.