1 files changed, 36 insertions, 22 deletions
diff --git a/theories/Init/Tactics.v b/theories/Init/Tactics.v
index f221aa8b42..d8590e4b59 100644
--- a/theories/Init/Tactics.v
+++ b/theories/Init/Tactics.v
@@ -13,6 +13,42 @@ Require Import Logic.
 
 (** Useful tactics *)
 
+(* A shorter name for generalize + clear, can be seen as an anti-intro *)
+
+Ltac revert H := generalize H; clear H.
+
+(* to contradict an hypothesis without copying its type. *)
+
+Ltac absurd_hyp h := 
+  let T := type of h in 
+  absurd T.
+
+(* Transforming a negative goal [ H:~A |- ~B ] into a positive one [ B |- A ]*)
+
+Ltac swap H := intro; apply H; clear H.
+
+(* A case with no loss of information. *)
+
+Ltac case_eq x := generalize (refl_equal x); pattern x at -1; case x.
+
+(* A tactic for easing the use of lemmas f_equal, f_equal2, ... *)
+
+Ltac f_equal := 
+  let cg := try congruence in
+  let r := try reflexivity in 
+  match goal with 
+   | |- ?f ?a = ?f' ?a' => cut (a=a'); [cg|r]
+   | |- ?f ?a ?b = ?f' ?a' ?b' => 
+      cut (b=b');[cut (a=a');[cg|r]|r]
+   | |- ?f ?a ?b ?c = ?f' ?a' ?b' ?c'=> 
+      cut (c=c');[cut (b=b');[cut (a=a');[cg|r]|r]|r]
+   | |- ?f ?a ?b ?c ?d= ?f' ?a' ?b' ?c' ?d'=> 
+      cut (d=d');[cut (c=c');[cut (b=b');[cut (a=a');[cg|r]|r]|r]|r]
+  | |- ?f ?a ?b ?c ?d ?e= ?f' ?a' ?b' ?c' ?d' ?e'=> 
+      cut (e=e');[cut (d=d');[cut (c=c');[cut (b=b');[cut (a=a');[cg|r]|r]|r]|r]|r]
+   | _ => idtac
+  end.
+
 (* Rewriting in all hypothesis. *)
 
 Ltac rewrite_all Eq := match type of Eq with
@@ -34,25 +70,3 @@ Ltac rewrite_all_rev Eq := match type of Eq with
  end.
 
 Tactic Notation "rewrite_all" "<-" constr(H) := rewrite_all_rev H.
-
-(* A case with no loss of information. *)
-
-Ltac case_eq x := generalize (refl_equal x); pattern x at -1; case x.
-
-(* A tactic for easing the use of lemmas f_equal, f_equal2, ... *)
-
-Ltac f_equal := 
-  let des := destruct 1 || intro in
-  let r := try reflexivity in 
-  match goal with 
-   | |- ?f ?a = ?f' ?a' => cut (a=a'); [des; r|r]
-   | |- ?f ?a ?b = ?f' ?a' ?b' => 
-      cut (b=b');[cut (a=a');[do 2 des; r|r]|r]
-   | |- ?f ?a ?b ?c = ?f' ?a' ?b' ?c'=> 
-      cut (c=c');[cut (b=b');[cut (a=a');[do 3 des; r|r]|r]|r]
-   | |- ?f ?a ?b ?c ?d= ?f' ?a' ?b' ?c' ?d'=> 
-      cut (d=d');[cut (c=c');[cut (b=b');[cut (a=a');[do 4 des; r|r]|r]|r]|r]
-  | |- ?f ?a ?b ?c ?d ?e= ?f' ?a' ?b' ?c' ?d' ?e'=> 
-      cut (e=e');[cut (d=d');[cut (c=c');[cut (b=b');[cut (a=a');[do 5 des; r|r]|r]|r]|r]|r]
-   | _ => idtac
-  end.