Little_Schemer.rkt

#lang scheme

(define atom?
  (lambda (x)
    (and (not (pair? x)) (not (null? x)))))

(define lat?
  (lambda (l)
    (cond
    ((null? l) #t)
    ((atom? (car l)) (lat? (cdr l)))
    (else #f))))

(lat? '(1 2 3 4))