include "basics/logic.ma".
include "ground_2/notation/xoa/false_0.ma".
include "ground_2/notation/xoa/true_0.ma".
+include "ground_2/notation/xoa/or_2.ma".
+include "ground_2/notation/xoa/and_2.ma".
include "ground_2/xoa/xoa.ma".
interpretation "logical false" 'false = False.
interpretation "logical true" 'true = True.
+
+(* Logical properties missing in the basic library **************************)
+
+lemma commutative_and: ∀A,B. A ∧ B → B ∧ A.
+#A #B * /2 width=1 by conj/
+qed-.