Path: utzoo!attcan!telly!eci386!jmm
From: jmm@eci386.uucp (John Macdonald)
Newsgroups: comp.lang.perl
Subject: Re: shortest self-reproducing Perl program
Message-ID: <1990Mar22.173813.8074@eci386.uucp>
Date: 22 Mar 90 17:38:13 GMT
References: <1990Mar20.203516.8429@iwarp.intel.com>
Reply-To: jmm@eci386.UUCP (John Macdonald)
Organization: Elegant Communications Inc., Toronto, Canada
Lines: 32

Rather than strain my brain, I let the computer find a short
self-reproducing perl "program" (well, it is a program in the
sense that its purpose in life is to be submitted to a Perl
interpreter to cause it to generate output, but it has no
other use).  The shell script to generate the program, and
the program it found, are:

---- cut here for genrepro sh script ----
: genrepro - generate a self-reproducing perl program
echo junk >cur.prog
echo trash >cur.out
until cmp -s cur.prog cur.out
do
    echo === not yet ===
    cat cur.out
    mv cur.out cur.prog
    perl cur.prog 2>cur.out
done

mv cur.out cur.prog

echo === final version ===
cat cur.prog
---- end of genrepro sh script ----
---- cut here for cur.prog ----
syntax error in file cur.prog at line 1, next 2 tokens "syntax error"
Execution aborted due to compilation errors.
---- end of cur.prog ----
-- 
Algol 60 was an improvment on most           | John Macdonald
of its successors - C.A.R. Hoare             |   jmm@eci386