From: hal9000@...
Date: 2000-07-19T20:55:34+00:00
Subject: [ruby-talk:04137] First quines in ruby?

Greetings, all.

This is a fairly frivolous post, so those of you in a big hurry can
skip it.

Maybe you are familiar with the practice of writing programs that
reproduce themselves. (I always liked Plauger's comment -- I think
it was Plauger -- who said, "This is often done in FORTRAN, for the
same reason that three-legged races are popular.")

The word "quine" comes from the mathematician Quine, by way of
Hofstadter's book _Goedel, Escher, Bach_.

My understanding is that any Turing-complete language is capable of
reproducing itself -- i.e., all but the most trivial and useless
languages. (I'm only repeating what I've heard -- I'm not that much
of a theorist.)

By the way, it is considered cheating to access a file (for example,
cat $(whence $0) in Kornshell) or to use a built-in listing feature
(like 10 LIST 10 in BASIC).

Anyway, I was curious as to whether it had been done in Ruby yet.
A search of the mailing list archive didn't turn up anything. So
unless someone speaks up, I claim the first one in Ruby.

Here are three different ones. The first is a ripoff of a famous
quine in C, working only on ASCII machines.

  s="s=%c%s%c; printf s,34,s,34,10%c"; printf s,34,s,34,10

The next one uses a here-document type of string.

  a=<<'EOF'
  print "a=<<'EOF'"
  print a
  print "EOF\n"
  print a
  EOF
  print "a=<<'EOF'"
  print a
  print "EOF\n"
  print a

The third one is a little more tricky and a little more fragile.

  $a=%w( def xx
  $a.each do |x| if x =~ /xx/
  print x+"\n" else print x, " " end end end; print "$a=%w( "; xx
  print ")\n"; xx
  )
  def xx
  $a.each do |x| if x =~ /xx/
  print x+"\n" else print x, " " end end end; print "$a=%w( "; xx
  print ")\n"; xx

That's all, folks. Have a great day!

Hal Fulton




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