Re: A Mandelbrot set generator in HG LISP

On 12 Apr 2025 14:01:00 GMT, Stefan Ram wrote:

From my recent postings in other newsgroups: A generator for
a Mandelbrot set image written in a LISP similar to the HG LISP I used
in 1981 on my Pet 2001 as I remember it.

Looks like a Lisp-1 dialect, rather than Lisp-2. But not a Scheme
derivative?

[extract kept as example, rest snipped]
>
(SETQ MANDELBROT
  (LAMBDA (X Y)
    (PROGN
      (SETQ C 126)
      (SETQ Z (LIST X Y))
      (SETQ A Z)
      (SETQ ITERATE
        (LAMBDA ()
          (COND ((OR (< C 32) (> (CABS Z) 2))
                 (- 126 C))
                (T
                 (PROGN
                   (SETQ TEMP-CMUL (CMUL Z Z))
                   (SETQ TEMP-CADD (CADD A TEMP-CMUL))
                   (SETQ Z TEMP-CADD)
                   (SETQ C (- C 1))
                   (ITERATE))))))
      (ITERATE))))

I was never a fan of “parenthesis pileup” layout. Try this for comparison:

(SETQ MANDELBROT
  (LAMBDA (X Y)
    (PROGN
      (SETQ C 126)
      (SETQ Z (LIST X Y))
      (SETQ A Z)
      (SETQ ITERATE
        (LAMBDA ()
          (COND
            ((OR (< C 32) (> (CABS Z) 2))
                 (- 126 C)
            )
            (T
              (PROGN
                (SETQ TEMP-CMUL (CMUL Z Z))
                (SETQ TEMP-CADD (CADD A TEMP-CMUL))
                (SETQ Z TEMP-CADD)
                (SETQ C (- C 1))
                (ITERATE)
              ) ; PROGN
            )
          ) ; COND
        ) ; LAMBDA
      ) ; ITERATE
      (ITERATE)
    ) ; PROGN
  ) ; LAMBDA
) ; MANDELBROT