little-schemer.rkt

;; Bits and pieces from reading The Little Schemer, implemented in Racket.

#lang racket

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

;; Returns whether the supplied s-expression is a list of atoms by
;; recursively checking each element of the input.
(define (lat? l)
  (cond
    ;; Base case -- we've reached the end of the expression.
    [(null? l) #t]
    ;; Break down the problem into smaller and smaller subsets of the
    ;; original expression.
    [(atom? (car l)) (lat? (cdr l))]
    ;; Short-circuit if we encounter an expression which is not an atom.
    [else #f]))