1 files changed, 24 insertions, 0 deletions
diff --git a/contrib/subtac/FixSub.v b/contrib/subtac/FixSub.v
index bbf722db..ded069bf 100644
--- a/contrib/subtac/FixSub.v
+++ b/contrib/subtac/FixSub.v
@@ -20,3 +20,27 @@ Definition Fix_sub (x : A) := Fix_F_sub x (Rwf x).
 End FixPoint.
 
 End Well_founded.
+
+Require Import Wf_nat.
+Require Import Lt.
+
+Section Well_founded_measure.
+Variable A : Set.
+Variable f : A -> nat.
+Definition R := fun x y => f x < f y.
+
+Section FixPoint.
+
+Variable P : A -> Set.
+
+Variable F_sub : forall x:A, (forall y: { y : A | f y < f x }, P (proj1_sig y)) -> P x.
+ 
+Fixpoint Fix_measure_F_sub (x : A) (r : Acc lt (f x)) {struct r} : P x :=
+   F_sub x (fun y: { y : A | f y < f x}  => Fix_measure_F_sub (proj1_sig y) 
+   (Acc_inv r (f (proj1_sig y)) (proj2_sig y))).
+
+Definition Fix_measure_sub (x : A) := Fix_measure_F_sub x (lt_wf (f x)).
+
+End FixPoint.
+
+End Well_founded_measure.