1 files changed, 46 insertions, 0 deletions
diff --git a/src/slalib/dvn.f b/src/slalib/dvn.f
new file mode 100644
index 0000000..37a4a6d
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+++ b/src/slalib/dvn.f
@@ -0,0 +1,46 @@
+      SUBROUTINE sla_DVN (V, UV, VM)
+*+
+*     - - - -
+*      D V N
+*     - - - -
+*
+*  Normalizes a 3-vector also giving the modulus (double precision)
+*
+*  Given:
+*     V       dp(3)      vector
+*
+*  Returned:
+*     UV      dp(3)      unit vector in direction of V
+*     VM      dp         modulus of V
+*
+*  If the modulus of V is zero, UV is set to zero as well
+*
+*  P.T.Wallace   Starlink   23 November 1995
+*
+*  Copyright (C) 1995 Rutherford Appleton Laboratory
+*-
+
+      IMPLICIT NONE
+
+      DOUBLE PRECISION V(3),UV(3),VM
+
+      INTEGER I
+      DOUBLE PRECISION W1,W2
+
+
+*  Modulus
+      W1=0D0
+      DO I=1,3
+         W2=V(I)
+         W1=W1+W2*W2
+      END DO
+      W1=SQRT(W1)
+      VM=W1
+
+*  Normalize the vector
+      IF (W1.LE.0D0) W1=1D0
+      DO I=1,3
+         UV(I)=V(I)/W1
+      END DO
+
+      END