proposition: Lemma or4P : reflect [\/ b1, b2, b3 | b4] [|| b1, b2, b3 | b4].
proof: Proof. case b1; first by constructor; constructor 1. case b2; first by constructor; constructor 2. case b3; first by constructor; constructor 3. case b4; first by constructor; constructor 4. by constructor; case. Qed.
imports: ssreflect ssrfun