;;; Recursive descent parser generator -- sample program
;;;
;;; (C) 2008 Gergő ÉRDI
;;; http://cactus.rulez.org/

(in-package :common-lisp-user)
(eval-when (:compile-toplevel :load-toplevel :execute)
  (require :lexer)
  (require :parser-recdesc))

(defpackage :cactus.parser-recdesc.example
  (:use :common-lisp :cactus.parser-recdesc :lexer)
  (:export :test))

(in-package :cactus.parser-recdesc.example)

(defparser expression-parser
    E
  (E     (T E^))
  (E^    ("+" T E^) ())
  (T     (F T^))
  (T^    ("*" F T^) ())
  (F     ("(" E ")") (int)))

(deflexer test-lexer
  ("[0-9]+"
   (return (values 'int (int %0))))
  ("[+*()]"
   (return %0))
  ("[:space:]+") )

(defun test (input)
  (labels ((terminal-matches? (terminal token)
	     (equal (car terminal) token)))
    (let* ((lex (test-lexer input))
	   (tokens (loop for foo = (multiple-value-list (funcall lex))
			 while (car foo)
			 collecting foo)))
      (pprint tokens)
      (pprint (expression-parser tokens #'terminal-matches?)))))

(eval-when (:execute)
  (test "(10 + 5) * 2"))