c  This program is an example of how to set up and use the
c  ran_cat() subroutine to generate random galaxy positions
c  in accord to a selected survey geometry and selection function.
c
c  To compile link with ran_subs.f and geometries.f
c  eg
c  f77 ran_subs.f geometries.f example.f -o example.exe
c
      program example
      implicit none
      integer iseed,i,N,j
      parameter(N=20000)
      real x(N),y(N),z(N),d(N),r(N)
      real zlimit
      character selfile*180,outfile*180
      logical vlim
c
c   Make Catalogue Selection
      selfile = 'data1/om1:lam0:strc:a/sel1.pscz '  !selection function file
      zlimit=0.5   !redshift at which to truncate the catalogue 
      iseed= -6969 !random number seed which should be negative
      outfile = 'data1/om1:lam0:strc:a/ran1.pscz'
      vlim=.false.
c
c   Generate N random galaxy positions and echo first 10
      do i=1,N
         call ran_cat(x(i),y(i),z(i),d(i),iseed,zlimit,selfile,vlim)
         r(i)=sqrt(x(i)**2+y(i)**2+z(i)**2)
         if (i.le.10) then
            write(0,'(i3,5(a,f7.4))') i,': x=',x(i),' y=',y(i),
     &        ' z=',z(i),' r=',r(i),' d=',d(i)
         end if
      end do
c
c
c  Write positions in the same format as one of the mock catalogues

      open(11,file=outfile,status='unknown',form='unformatted')
      write(11) 0,N     ! n=0  and ng=number of galaxies in the catalogue
      write(11) zlimit     
      write(11) 2      ! idf=2
      write(11) 0.0,0.0,0.0,((0.0,i=1,3),j=1,3),iseed,
     &     0.0,0.0,0.0          !dummy values for
c                                      !orientation and velocity of the 
c                                      !observer in the N-body simulation
      write(11) 0,0,0             !dummy values for mass fluctuation 
c                     !in 8Mpc/h, density parameter and cosmological constant
      write(11) (x(i),i=1,N)
      write(11) (y(i),i=1,N)
      write(11) (z(i),i=1,N)
      write(11) (d(i),i=1,N)
      write(11) (0.0,i=1,N)  !dummy magnitude values
      write(11) (0.0,i=1,N)  !dummy zhmax values
      write(11) (0,i=1,N)    !dummy id values
      close(11)

      stop
      end