euler 1

gistfile1.lisp

(define null ())

(define range  
    (lambda (x)  
        (cond  
            ((= x 0) (cons 0 null))  
            (else  
                (cons x (range (- x 1)))))))

(define sum  
    (lambda (list) 
        (cond 
            ((null? list) 0) 
            (else (+ (car list) (sum (cdr list)))))))

(define divisible?
    (lambda (x)
        (cond
            ((or (= (mod x 5) 0) (= (mod x 3) 0)) #t)
            (else #f))))

(define filter
    (lambda (list predicate)
        (cond
            ((null? list) null)
            ((predicate (car list)) (cons (car list) (filter (cdr list) predicate)))
            (else (filter (cdr list) predicate)))))

(sum (filter (range 999) divisible?))