mandelbrot

actualmandel.cbl

*> vim: set syntax= et sts=2 sw=2 :
*> free syntax. compile like so:
*>   cobc -x -free -o actualmandel actualmandel.cbl
identification division.
  program-id. actualmandel.
environment division.
data division.
  working-storage section.
    01 template-string.
      03 template-elems occurs 10 times pic x.
    01 output-string.
      03 output-elems occurs 97 times pic x.
    01 base-r pic 9(5).
    01 base-i pic 9(5).
    01 iter-index pic 9(5).
    01 iter-div pic 9(5).
    01 iter-rem pic 9(5).
    01 dist2 pic 9(10)V9(9).
    01 zoom  pic 9(10)V9(9).
    01 zr    pic S9(5)V9(9).
    01 zi    pic S9(5)V9(9).
    01 cr    pic S9(5)V9(9).
    01 ci    pic S9(5)V9(9).
    01 tr    pic S9(5)V9(9).
    01 ti    pic S9(5)V9(9).
  
procedure division.
  display "start"
  move " .,;:|$%#@" to template-string
  move 1.2 to zoom
  move 0 to base-i
  perform until base-i > 40
    compute ci = (((base-i / 40.000) * 2.0) - 1.0) * zoom
    move 0 to base-r
    perform until base-r > 96
      compute cr = (((base-r / 96.000) * 2.0) - 1.5) * zoom
      move " " to output-elems(base-r)
      perform iter-start thru iter-end
      add 1 to base-r
    end-perform
    display output-string
    add 1 to base-i
  end-perform
  display "done"
stop run.

iter-start.
  move 0 to zr
  move 0 to zi
  move 0 to iter-index
  perform until iter-index >= 1000
    compute tr = ((zr * zr) - (zi * zi) + cr)
    compute ti = ((2 * zr * zi) + ci)
    move tr to zr
    move ti to zi
    compute dist2 = (zr * zr) + (zi * zi)
    if dist2 > 4.0
      go to iter-end
    end-if
    add 1 to iter-index
  end-perform.
iter-end.
  if iter-index < 1000 then
    perform until iter-index < 10
      subtract 10 from iter-index
    end-perform
    add 1 to iter-index
    move template-elems(iter-index) to output-elems(base-r)
  end-if
  exit.