let-opt

(define-syntax let-optionals
  (syntax-rules ()
    ((_ args ((var default) rest ... . restarg) body ...)
     (let* ((tmp args)
            (var (if (null? tmp) default (car tmp))))
       (let-optionals (if (null? tmp) '() (cdr tmp))
                      (rest ... . restarg)
                      body ...)))
    ((_ args () body ...)
     (begin body ...))
    ((_ args restarg body ...)
     (let ((restarg args))
       body ...))))

(define-syntax let-optionals*
  (lambda(stx)
    (define (add-default spec)
      (syntax-case spec ()
        ((var default) #'(var default))
        (var #'(var #f))))
    (syntax-case stx ()
      ((_ args (spec ... . restarg) body0 body1 ...)
       #`(let-optionals args (#,@(map add-default #'(spec ...)) . restarg)
            body0 body1 ...)))))