;;;; Definitions of macros

;;; From SRFI 8
(define-syntax receive
  (syntax-rules ()
    ((receive formals expression body ...)
     (call-with-values (lambda () expression)
                       (lambda formals body ...)))))

;;; Shivers-compatible let-optionals*
;;; This version from Scheme-48 1.9.2,
;;; using error instead of assertion-violation
(define-syntax let-optionals*
  (syntax-rules ()
    ((let-optionals* arg (opt-clause ...) body ...)
     (let ((rest arg))
       (%let-optionals* rest (opt-clause ...) body ...)))))

(define-syntax %let-optionals*
  (syntax-rules ()
    ((%let-optionals* arg (((var ...) xparser) opt-clause ...) body ...)
     (call-with-values (lambda () (xparser arg))
       (lambda (rest var ...)
         (%let-optionals* rest (opt-clause ...) body ...))))

    ((%let-optionals* arg ((var default) opt-clause ...) body ...)
     (call-with-values (lambda () (if (null? arg) (values default '())
				      (values (car arg) (cdr arg))))
       (lambda (var rest)
	 (%let-optionals* rest (opt-clause ...) body ...))))

    ((%let-optionals* arg ((var default test) opt-clause ...) body ...)
     (call-with-values (lambda ()
			 (if (null? arg) (values default '())
			     (let ((var (car arg)))
			       (if test (values var (cdr arg))
				   (error "arg failed LET-OPT test" var)))))
       (lambda (var rest)
	 (%let-optionals* rest (opt-clause ...) body ...))))

    ((%let-optionals* arg ((var default test supplied?) opt-clause ...) body ...)
     (call-with-values (lambda ()
			 (if (null? arg) (values default #f '())
			     (let ((var (car arg)))
			       (if test (values var #t (cdr arg))
				   (error "arg failed LET-OPT test" var)))))
       (lambda (var supplied? rest)
	 (%let-optionals* rest (opt-clause ...) body ...))))

    ((%let-optionals* arg (rest) body ...)
     (let ((rest arg)) body ...))

    ((%let-optionals* arg () body ...)
     (if (null? arg) (begin body ...)
	 (error "Too many arguments in let-opt" arg)))))