!
      program f90merge
      implicit none
      real :: tsource,fsource,x
      integer :: i,n
!
      n = 1000000
      tsource = 1.
      fsource = 0.
      x = 0.
      do i=1,n
        x = merge(tsource,fsource, x < 200.) 
!       if (x < 200.) then
!         x = tsource
!       else
!         x = fsource
!       endif
      enddo
      end program f90merge