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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.lang.lisp
Subject: Re: A Mandelbrot set generator in HG LISP
Date: Sun, 13 Apr 2025 00:13:26 -0000 (UTC)
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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