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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
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