1 files changed, 42 insertions, 0 deletions
diff --git a/src/Util/ZUtil/Tactics/SplitMinMax.v b/src/Util/ZUtil/Tactics/SplitMinMax.v
new file mode 100644
index 000000000..901cfde88
--- /dev/null
+++ b/src/Util/ZUtil/Tactics/SplitMinMax.v
@@ -0,0 +1,42 @@
+Require Import Coq.omega.Omega.
+Require Import Coq.ZArith.BinInt.
+
+Ltac rewrite_min_max_side_condition_t := omega.
+
+Ltac revert_min_max :=
+  repeat match goal with
+         | [ H : context[Z.min _ _] |- _ ] => revert H
+         | [ H : context[Z.max _ _] |- _ ] => revert H
+         end.
+Ltac rewrite_min_max_step_fast :=
+  match goal with
+  | [ H : (?a <= ?b)%Z |- context[Z.max ?a ?b] ]
+    => rewrite (Z.max_r a b) by assumption
+  | [ H : (?b <= ?a)%Z |- context[Z.max ?a ?b] ]
+    => rewrite (Z.max_l a b) by assumption
+  | [ H : (?a <= ?b)%Z |- context[Z.min ?a ?b] ]
+    => rewrite (Z.min_l a b) by assumption
+  | [ H : (?b <= ?a)%Z |- context[Z.min ?a ?b] ]
+    => rewrite (Z.min_r a b) by assumption
+  end.
+Ltac rewrite_min_max_step :=
+  match goal with
+  | _ => rewrite_min_max_step_fast
+  | [ |- context[Z.max ?a ?b] ]
+    => first [ rewrite (Z.max_l a b) by rewrite_min_max_side_condition_t
+             | rewrite (Z.max_r a b) by rewrite_min_max_side_condition_t ]
+  | [ |- context[Z.min ?a ?b] ]
+    => first [ rewrite (Z.min_l a b) by rewrite_min_max_side_condition_t
+             | rewrite (Z.min_r a b) by rewrite_min_max_side_condition_t ]
+  end.
+Ltac only_split_min_max_step :=
+  match goal with
+  | _ => revert_min_max; progress repeat apply Z.min_case_strong; intros
+  | _ => revert_min_max; progress repeat apply Z.max_case_strong; intros
+  end.
+Ltac split_min_max_step :=
+  match goal with
+  | _ => rewrite_min_max_step
+  | _ => only_split_min_max_step
+  end.
+Ltac split_min_max := repeat split_min_max_step.