Ex2.3 英語以外の文法でgenerate

PAIP Common Lisp

r5rsの内容をちょっとコピーしてみる。
ただし、実行するとスタックオーバーフローする。< だめじゃん…。

;;; Exercise 2.3 [h] Write a trivial grammar for some other language. This can be a
;;; natural language other than English, or perhaps a subset of computer language.
(defvar *scheme-subset-grammar*)
(setf *scheme-subset-grammar*
  '((<expression> -> <variable> <literal> <procedure-call>
                     <lambda-expression> <conditional>)
    (<literal> -> <self-evaluating>)
    (<self-evaluating> -> <boolean> <number> <character> <string>)

    (<procedure-call> -> (|(| <operator> <operand>* |)|))
    (<operator> -> <expression>)
    (<operand>* -> () (<operand> <operand>*))
    (<operand> -> <expression>)

    (<lambda-expression> -> (|(| lambda <formals> <body> |)|))
    (<formals> -> (|(| <variable>* |)|) <variable> 
                  (|(| <variable>+ |.| <variable> |)|))
    (<body> -> (<sequence>))
    (<sequence> -> (<command>* <expression>))
    (<command>* -> () (<command> <command>*))
    (<command> -> <expression>)

    (<conditional> -> (|(| if <test> <consequent> <alternate> |)|))
    (<test> -> <expression>)
    (<consequent> -> <expression>)
    (<alternate> -> <expression> <empty>)

    (<empty> -> ())
    (<variable>+ -> (<variable> <variable>*))
    (<variable>* -> () (<variable> <variable>*))

    ;; simple case
    (<variable> -> x y z a b c d e f g)
    (<boolean>  -> |#f| |#t|) 
    (<number> -> 0 1 2 3 4 5 6 7 8 9)
    (<character> -> |#\a| |#\b|)
    (<string> -> "foo" "bar" "bazz")
))

(setf *grammar* *scheme-subset-grammar*)
(format nil "~a" (generate '<expression>))