c===========================================================
c     Computes and reports estimate of machine epsilon.
c
c     Recall: machine epsilon is smallest positive 'eps' 
c     such that 
c
c             (1.0d0 + eps ) .ne. (1.0d0)
c
c     Program accepts optional argument which specifies 
c     division factor: values close to 1.0 will result 
c     in more accurate estimate of machine epsilon.
c===========================================================
      program         meps

      implicit        none

c-----------------------------------------------------------
c     Note use of 'r8arg', available in 'libp410f.a' which
c     works exactly like 'i4arg' except that it returns 
c     a real*8 value parsed from the specified command-line
c     argument
c-----------------------------------------------------------
      real*8          r8arg

      real*8          default_fac
      parameter     ( default_fac = 2.0d0 )

      real*8          eps,         neweps,        fac

      fac = r8arg(1,default_fac)
      write(0,*) 'meps: using division factor: ', fac

      eps    = 1.0d0
      neweps = 1.0d0
      do while( .true. )
         if( 1.0d0 .eq. (1.0d0 + neweps) ) then
            write(*,*) eps
            stop
         else
            eps    = neweps
            neweps = neweps / fac
         end if
      end do

      stop

      end