;; Datum grammar acceptors.

;; Copyright (c) 2007 David Van Horn
;; Licensed under the Academic Free License version 3.0

;; <dvanhorn@cs.brandeis.edu>

(module grammar mzscheme
  (require-for-syntax "grammar-procedures.ss"
                      "grammar-predicate.ss")
  (require "grammar-procedures.ss")
  
  (provide (all-from "grammar-procedures.ss"))
  (provide grammar define-grammar)
  
  (define-syntax (grammar stx)
    (syntax-case stx ()
      ((_ start (i v ...) ...)
       (and (memq (syntax-object->datum (syntax start))
                  (syntax-object->datum (syntax (i ...))))
            (grammar? (syntax-object->datum stx)))
         (syntax (letrec ((i (lambda (x) ((seq v ...) x))) ...)
                   (cfa->predicate start))))))

  (define-syntax (define-grammar stx)
    (syntax-case stx ()
      ((_ pred? (grammar start (i v ...) ...))
       (and (memq (syntax-object->datum (syntax start))
                  (syntax-object->datum (syntax (i ...))))
            (grammar? (syntax-object->datum (syntax (grammar start (i v ...) ...)))))
       (syntax (define-values (pred? i ...)
                 (letrec ((i (lambda (x) ((seq v ...) x)))
                          ...)
                   (values
                    (cfa->predicate start)
                    i ...)))))))
                 
  ) ; end of module grammar