(* *)
(**************************************************************************)
-include "ground/notation/relations/white_harrow_2.ma".
+include "ground/notation/relations/arroweq_2.ma".
include "ground/lib/subset_inclusion.ma".
(* EQUIVALENCE FOR SUBSETS **************************************************)
interpretation
"equivalence (subset)"
- 'WhiteHArrow u1 u2 = (subset_eq ? u1 u2).
+ 'ArrowEq u1 u2 = (subset_eq ? u1 u2).
+
+(* Basic destructions *******************************************************)
+
+lemma subset_in_eq_repl_back (A) (a:A):
+ âu1. a Ï” u1 â âu2. u1 â u2 â a Ï” u2.
+#A #a #u1 #Hu1 #u2 *
+/2 width=1 by/
+qed-.
+
+lemma subset_in_eq_repl_fwd (A) (a:A):
+ âu1. a Ï” u1 â âu2. u2 â u1 â a Ï” u2.
+#A #a #u1 #Hu1 #u2 *
+/2 width=1 by/
+qed-.
(* Basic constructions ******************************************************)