! ----------------------------------------------
! Example program
!
! Complex arithmetics, applied to Mandelbrot set 
! Complex plane box corners (x0,y0) to (x1,y1)
! ----------------------------------------------
program mandel
  implicit none
  integer, parameter:: dp=kind(1.d0),ix=10000
  real(dp),parameter:: d=1.d-2,x0=-1.5d0,x1=0.5d0,y0=-1.d0,y1=1.d0
  integer:: i
  complex(dp):: cx,c
  real(dp):: x,y  
  x = x0
  do 
     y = y0
     do
        c  = cmplx(x,y,dp)
        cx = c
        do  i = 1, ix
           cx = cx**2+c           
           if(abs(cx)>2) exit 
        end do
        write(12,'(2f8.3,i10)') c,i
        y = y + d
        if(y>y1) exit
     end do
     write(12,*) 
     x = x + d
     write(*,'(f0.1," percent done")') (x-x0)/(x1-x0)*100.d0
     if(x>x1) exit
  end do
end program mandel