From b341c644ed7ad52779b148e7ba6e3dd9158c2174 Mon Sep 17 00:00:00 2001
From: herbelin
Date: Sat, 16 Jul 2011 20:35:17 +0000
Subject: Tentative abbreviation "rew Heq in H" for eq_rect. (feedback welcome)

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@14281 85f007b7-540e-0410-9357-904b9bb8a0f7
---
 CHANGES                      | 1 +
 theories/Init/Logic.v        | 7 +++++++
 theories/Vectors/VectorDef.v | 8 ++++----
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/CHANGES b/CHANGES
index d02e29e4d0..530e25096a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -86,6 +86,7 @@ Libraries
   Vcons become Vector.cons. You can use notations by importing
   Vector.VectorNotations.
 - Removal of TheoryList. Requiring List instead should work most of the time.
+- New syntax "rew Heq in H" and "rew <- Heq in H" for eq_rect and eq_rect_r.
 
 Internal infrastructure
 
diff --git a/theories/Init/Logic.v b/theories/Init/Logic.v
index 8551ca97dc..82d2e04d77 100644
--- a/theories/Init/Logic.v
+++ b/theories/Init/Logic.v
@@ -331,6 +331,13 @@ Section Logic_lemmas.
   Defined.
 End Logic_lemmas.
 
+Notation "'rew' H 'in' H'" := (eq_rect _ _ H' _ H)
+  (at level 0, H' at level 9).
+Notation "'rew' <- H 'in' H'" := (eq_rect_r _ H' H)
+  (at level 0, H' at level 9).
+Notation "'rew' -> H 'in' H'" := (eq_rect _ _ H' _ H)
+  (at level 0, H' at level 9, only parsing).
+
 Theorem f_equal2 :
   forall (A1 A2 B:Type) (f:A1 -> A2 -> B) (x1 y1:A1)
     (x2 y2:A2), x1 = y1 -> x2 = y2 -> f x1 x2 = f y1 y2.
diff --git a/theories/Vectors/VectorDef.v b/theories/Vectors/VectorDef.v
index 777e68b45b..adc2c09a31 100644
--- a/theories/Vectors/VectorDef.v
+++ b/theories/Vectors/VectorDef.v
@@ -197,18 +197,18 @@ Fixpoint rev_append_tail {A n p} (v : t A n) (w: t A p)
   | a :: v' => rev_append_tail v' (a :: w)
   end.
 
+Import EqdepFacts.
+
 (** This one has a better type *)
 Definition rev_append {A n p} (v: t A n) (w: t A p)
   :t A (n + p) :=
-eq_rect _ (fun n => t A n) (rev_append_tail v w) _
-  (eq_sym _ _ _ (plus_tail_plus n p)).
+  rew <- (plus_tail_plus n p) in (rev_append_tail v w).
 
 (** rev [a₁ ; a₂ ; .. ; an] is [an ; a{n-1} ; .. ; a₁]
 
 Caution : There is a lot of rewrite garbage in this definition *)
 Definition rev {A n} (v : t A n) : t A n :=
- eq_rect _ (fun n => t A n) (rev_append v [])
-   _ (eq_sym _ _ _ (plus_n_O _)).
+ rew <- (plus_n_O _) in (rev_append v []).
 
 End BASES.
 Local Notation "v [@ p ]" := (nth v p) (at level 1).
-- 
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