double precision function DRANU()
c Copyright (c) 1996 California Institute of Technology, Pasadena, CA.
c ALL RIGHTS RESERVED.
c Based on Government Sponsored Research NAS7-03001.
c>> 1994-10-20 DRANU Krogh  Changes to use M77CON
c>> 1994-06-24 DRANU CLL Changed common to use RANC[D/S]1 & RANC[D/S]2.
c>> 1992-03-16 CLL
c>> 1991-11-26 CLL Reorganized common. Using RANCM[A/D/S].
c>> 1991-11-22 CLL Added call to RAN0, and DGFLAG in common.
c>> 1991-01-15 CLL Reordered common contents for efficiency.
C>> 1990-01-23 CLL  Making names in common same in all subprogams.
C>> 1987-04-22 DRANU  Lawson  Initial code.
c        Returns one pseudorandom number from the uniform distribution
c        on [0., 1.].
c     C. L. Lawson & S. Y. Chiu, JPL, Apr 1987.
c     ------------------------------------------------------------------
c--D replaces "?": ?RANU, ?RANUA, RANC?1, RANC?2, ?PTR, ?NUMS, ?GFLAG
C     RANCD1 and RANCD2 are common blocks.
c     Calls RAN0 to initialize DPTR and DGFLAG.
c     ------------------------------------------------------------------
      integer M
      parameter(M = 97)
      double precision DNUMS(M)
      common/RANCD2/DNUMS
c
      integer DPTR
      logical DGFLAG
      common/RANCD1/DPTR, DGFLAG
      save  /RANCD1/, /RANCD2/, FIRST
      logical FIRST
      data    FIRST / .true. /
c     ------------------------------------------------------------------
      if(FIRST) then
         FIRST = .false.
         call RAN0
      endif
c
      DPTR = DPTR - 1
      if(DPTR .eq. 0) then
         call DRANUA(DNUMS, M)
         DPTR = M
      endif
      DRANU = DNUMS(DPTR)
      return
      end