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slalib/sepv.f

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+      REAL FUNCTION sla_SEPV (V1, V2)
+*+
+*     - - - - -
+*      S E P V
+*     - - - - -
+*
+*  Angle between two vectors.
+*
+*  (single precision)
+*
+*  Given:
+*     V1      r(3)    first vector
+*     V2      r(3)    second vector
+*
+*  The result is the angle, in radians, between the two vectors.  It
+*  is always positive.
+*
+*  Notes:
+*
+*  1  There is no requirement for the vectors to be unit length.
+*
+*  2  If either vector is null, zero is returned.
+*
+*  3  The simplest formulation would use dot product alone.  However,
+*     this would reduce the accuracy for angles near zero and pi.  The
+*     algorithm uses both cross product and dot product, which maintains
+*     accuracy for all sizes of angle.
+*
+*  Called:  sla_DSEPV
+*
+*  Last revision:   7 May 2000
+*
+*  Copyright P.T.Wallace.  All rights reserved.
+*
+*  License:
+*    This program is free software; you can redistribute it and/or modify
+*    it under the terms of the GNU General Public License as published by
+*    the Free Software Foundation; either version 2 of the License, or
+*    (at your option) any later version.
+*
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU General Public License for more details.
+*
+*    You should have received a copy of the GNU General Public License
+*    along with this program (see SLA_CONDITIONS); if not, write to the 
+*    Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
+*    Boston, MA  02111-1307  USA
+*
+*-
+
+      IMPLICIT NONE
+
+      REAL V1(3),V2(3)
+
+      INTEGER I
+      DOUBLE PRECISION DV1(3),DV2(3)
+      DOUBLE PRECISION sla_DSEPV
+
+
+
+*  Use double precision version.
+      DO I=1,3
+         DV1(I) = DBLE(V1(I))
+         DV2(I) = DBLE(V2(I))
+      END DO
+      sla_SEPV = REAL(sla_DSEPV(DV1,DV2))
+
+      END