資料來源 : WordNet®

Quine
     n : United States philosopher and logician who championed an
         empirical view of knowledge that depended on language
         (1908-2001) [syn: {W. V. Quine}, {Willard Van Orman Quine}]

資料來源 : Free On-Line Dictionary of Computing

quine
     
         /kwi:n/ (After the logician Willard V. Quine,
        via Douglas Hofstadter) A program that generates a copy of its
        own source text as its complete output.  Devising the shortest
        possible quine in some given programming language is a common
        hackish amusement.
     
        In most interpreted languages, any constant, e.g. 42, is a
        quine because it "evaluates to itself".  In certain {Lisp}
        dialects (e.g. {Emacs Lisp}), the symbols "nil" and "t" are
        "self-quoting", i.e. they are both a symbol and also the value
        of that symbol.  In some dialects, the function-forming
        function symbol, "lambda" is self-quoting so that, when
        applied to some arguments, it returns itself applied to those
        arguments.  Here is a quine in {Lisp} using this idea:
     
         ((lambda (x) (list x x)) (lambda (x) (list x x)))
     
        Compare this to the {lambda expression}:
     
        	(\ x . x x) (\ x . x x)
     
        which reproduces itself after one step of {beta reduction}.
        This is simply the result of applying the {combinator} {fix}
        to the {identity function}.  In fact any quine can be
        considered as a {fixed point} of the language's evaluation
        mechanism.
     
        We can write this in {Lisp}:
     
         ((lambda (x) (funcall x x)) (lambda (x) (funcall x x)))
     
        where "funcall" applies its first argument to the rest of its
        arguments, but evaluation of this expression will never
        terminate so it cannot be called a quine.
     
        Here is a more complex version of the above Lisp quine, which
        will work in Scheme and other Lisps where "lambda" is not
        self-quoting:
     
         ((lambda (x)
           (list x (list (quote quote) x)))
          (quote
             (lambda (x)
               (list x (list (quote quote) x)))))
     
        It's relatively easy to write quines in other languages such
        as {PostScript} which readily handle programs as data; much
        harder (and thus more challenging!) in languages like {C}
        which do not.  Here is a classic {C} quine for {ASCII}
        machines:
     
         char*f="char*f=%c%s%c;main() {printf(f,34,f,34,10);}%c";
         main(){printf(f,34,f,34,10);}
     
        For excruciatingly exact quinishness, remove the interior line
        break.  Some infamous {Obfuscated C Contest} entries have been
        quines that reproduced in exotic ways.
     
        {Ken Thompson}'s {back door} involved an interesting variant
        of a quine - a compiler which reproduced part of itself when
        compiling (a version of) itself.
     
        [{Jargon File}]
     
        (1995-04-25)