#lang scheme/base

(provide first second third fourth fifth sixth seventh eighth ninth tenth
         last

         rest

         cons?
         empty
         empty?)

(define (first x)
  (if (and (pair? x) (list? x))
    (car x)
    (raise-type-error 'first "non-empty list" x)))

(define-syntax define-lgetter
  (syntax-rules ()
    [(_ name npos)
     (define (name l0)
       (if (list? l0)
         (let loop ([l l0] [pos npos])
           (if (pair? l)
             (if (eq? pos 1) (car l) (loop (cdr l) (sub1 pos)))
             (raise-type-error
              'name (format "list with ~a or more items" npos) l0)))
         (raise-type-error 'name "list" l0)))]))
(define-lgetter second  2)
(define-lgetter third   3)
(define-lgetter fourth  4)
(define-lgetter fifth   5)
(define-lgetter sixth   6)
(define-lgetter seventh 7)
(define-lgetter eighth  8)
(define-lgetter ninth   9)
(define-lgetter tenth   10)

(define (last l)
  (if (and (pair? l) (list? l))
    (let loop ([l l])
      (if (pair? (cdr l))
        (loop (cdr l))
        (car l)))
    (raise-type-error 'last "non-empty list" l)))

(define (rest l)
  (if (and (pair? l) (list? l))
    (cdr l)
    (raise-type-error 'rest "non-empty list" l)))

(define cons? (lambda (l) (pair? l)))
(define empty? (lambda (l) (null? l)))
(define empty '())