(load "chez-init.ss")

(define-datatype expression expression?
  (var-exp
   (id symbol?))
  (lambda-exp
   (id symbol?)
   (body expression?))
  (app-exp
   (rator expression?)
   (rand expression?)))

(define parse
  (lambda (exp)
    (cond [(symbol? exp) (var-exp exp)]
	  [(pair? exp)
	   (cond [(eq? (car exp) 'lambda)
		  (lambda-exp (caadr exp) (parse (caddr exp)))]
		 [(> (length exp) 2)
		  (eopl:error 'parse
			      "Invalid concrete syntax ~s" exp)]
		 [else (app-exp (parse (car exp)) (parse (cadr exp)))])]
	  [(eopl:error 'parse
		       "Invalid concrete syntax ~s" exp)])))







	   

(define parse-expression
  (lambda (datum)
    (cond [(symbol? datum) (var-exp datum)]
	  [(pair? datum)
	   (if (eqv? (car datum) 'lambda)
	       (lambda-exp (caadr datum)
			   (parse-expression (caddr datum)))
	       (app-exp
		(parse-expression (car datum))
		(parse-expression (cadr datum))))]
	  [else (eopl:error 'parse-expression
			    "Invalid concrete syntax ~s" datum)])))










(define unparse-expression
  (lambda (exp)
    (cases expression exp
	   [var-exp (id) id]
	   [lambda-exp (id body)
		       (list 'lambda (list id)
			     (unparse-expression body))]
	   [app-exp (rator rand)
		    (list (unparse-expression rator)
			  (unparse-expression rand))])))























(define unparse-expression-pseudo-java
  (lambda (exp)
    (cases expression exp
	   (var-exp (id) (symbol->string id))
	   (lambda-exp (id body)
		       (string-append "unnamed ("
			     (symbol->string id)
			     ") {"
			     (unparse-expression-pseudo-java body)
			     "}"))
	   (app-exp (rator rand)
		    (string-append (unparse-expression-pseudo-java rator)
				   "("
			           (unparse-expression-pseudo-java rand)
				   ");")))))