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From: greid@adobe.com (Glenn Reid)
Newsgroups: comp.windows.news
Subject: Re: A PostScript Quine (a followup)
Keywords: Quine, useless trivia
Message-ID: <1194@adobe.UUCP>
Date: 14 Sep 89 20:23:43 GMT
References: <17620@bellcore.bellcore.com>
Sender: news@adobe.COM
Reply-To: greid@adobe.COM (Glenn Reid)
Organization: Adobe Systems Incorporated, Mountain View
Lines: 27

In article <17620@bellcore.bellcore.com> sjs@bellcore.com (Stan Switzer) writes:
> A "quine" is a program which when evaluated yields its own
> representation.  A quine can be formally described as a fixed point of
> a language's denotation function.  Trivial evaluations (e.g.:
> literals) are excluded and the program cannot require any input data
> (e.g.: "cat cat.c").
>
> For the heck of it, let's say a PostScript quine is a procedure
> "{...}" which when followed by "n { exec } repeat" yields the same (or
> equivalent) value for any non-negative integer value of "n"
> (including 0).
> The shortest I have found for PostScript is
>
>  {{[ exch /dup load /exec load ] cvx} dup exec}

Wait--now I get it.  The execution of the procedure has to give
you the same procedure back.  I was lost in the definition of
"quine".  According to the way you've set it up (using "n { exec } repeat"),
the following should qualify:

    {/exec{dup}def}

I guess this doesn't qualify, since it only works if you invoke it
with "exec", and (only after the first invocation :-), but it sure
is short...

Glenn Reid