Merge branch 'robbert/multiset_solver' into 'master'

Add solver `multiset_solver` for multisets

See merge request !167

CHANGELOG.md

@@ -20,6 +20,7 @@ API-breaking change is listed.
 - Rename `drop_insert` into `drop_insert_gt` and add `drop_insert_le`.
 - Added `Countable` instance for `Ascii.ascii`.
 - Make lemma `list_find_Some` more apply friendly.
+- Add tactic `multiset_solver` for solving goals involving multisets.
 
 ## std++ 1.3 (released 2020-03-18)
 

tests/multiset_solver.v

+From stdpp Require Import gmultiset.
+
+Section test.
+  Context `{Countable A}.
+  Implicit Types x y : A.
+  Implicit Types X Y : gmultiset A.
+
+  Lemma test1 x y X : {[x]} ⊎ ({[y]} ⊎ X) ≠ ∅.
+  Proof. multiset_solver. Qed.
+  Lemma test2 x y X : {[x]} ⊎ ({[y]} ⊎ X) = {[y]} ⊎ ({[x]} ⊎ X).
+  Proof. multiset_solver. Qed.
+  Lemma test3 x : {[x]} ⊎ ∅ ≠@{gmultiset A} ∅.
+  Proof. multiset_solver. Qed.
+  Lemma test4 x y z X Y :
+    {[z]} ⊎ X = {[y]} ⊎ Y →
+    {[x]} ⊎ ({[z]} ⊎ X) = {[y]} ⊎ ({[x]} ⊎ Y).
+  Proof. multiset_solver. Qed.
+  Lemma test5 X x : X ⊎ ∅ = {[x]} → X ⊎ ∅ ≠@{gmultiset A} ∅.
+  Proof. multiset_solver. Qed.
+End test.