#!/usr/bin/guile \
-e main -s
!#

(import (srfi srfi-28))

(define (mandelbrot f top-left bottom-right step max-iter)
  (define (mb c)
    (do ((i 0 (1+ i))
	 (z 0 (f z c)))
	((or (<= max-iter i)
	     (> (magnitude z) 2))
	 (write-char (integer->char i)))))
  (display (format
	    "P5 ~a ~a ~a "
	    (inexact->exact (/ (real-part (- bottom-right top-left)) step))
	    (inexact->exact (/ (imag-part (- top-left bottom-right)) step))
	    max-iter))
  (do ((y (imag-part top-left) (- y step)))
      ((<= y (imag-part bottom-right)))
    (do ((x (real-part top-left) (+ x step)))
	((>= x (real-part bottom-right)))
      (mb (make-rectangular x y)))))

(define (main args)
  (mandelbrot (lambda (z c) (+ (* z z) c))
	      -2+1i +1-1i 1/1000 16))