GEANT321/ghits/gcubs.F

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.1  1995/10/24 10:21:08  cernlib
   6 * Geant
   7 *
   8 *
   9 #include "geant321/pilot.h"
  10 *CMZ :  3.21/02 29/03/94  15.41.20  by  S.Giani
  11 *-- Author :
  12       SUBROUTINE GCUBS(X,Y,D1,D2,A)
  13 C.
  14 C.
  15 C.    ******************************************************************
  16 C.    *                                                                *
  17 C.    *       Calculates a cubic through P1,(-X,Y1),(X,Y2),P2          *
  18 C.    *       where Y2=-Y1                                             *
  19 C.    *        Y=A(1)+A(2)*X+A(3)*X**2+A(4)*X**3                       *
  20 C.    *        The coordinate system is assumed to be the cms system   *
  21 C.    *        of P1,P2.                                               *
  22 C.    *                                                                *
  23 C.    *    ==>Called by : GIPLAN,GICYL                                 *
  24 C.    *       Author    H.Boerner  *********                           *
  25 C.    *                                                                *
  26 C.    ******************************************************************
  27 C.
  28       REAL X,Y,D1,D2,A(4)
  29 C.
  30 C.
  31 C.    ------------------------------------------------------------------
  32 C.
  33 C.
  34       IF (X.EQ.0.)                               GO TO 10
  35 C
  36 C
  37       FACT   = (D1 - D2) * 0.25
  38       A(1)   = - 1. * FACT * X
  39       A(3)   = FACT / X
  40       A(2)   = (6. * Y - (D1 + D2) * X) / (4. * X)
  41       A(4)   = ((D1 + D2)*X - 2.*Y) / (4.*X**3)
  42       RETURN
  43 C
  44   10  A(1)   = 0.
  45       A(2)   = 1.
  46       A(3)   = 0.
  47       A(4)   = 0.
  48       END