#lang scheme
(define mylist '(1 2 3 d f g 4 3 2 1))

(define print-numbers
  (lambda (l)
    (cond ((null? l) (void))
          ((number? (car l))
           (print (car l))
           (print-numbers (cdr l)))
          (else
           (print-numbers (cdr l))))))

(define print-numbers2
  (lambda (l)
    (for-each 
     (lambda (item)
       (when (number? item) (print item)))
     l)))

(define numbers-in 
  (lambda (l)
    (filter number? l)))

(define print-numbers3
  (lambda (l)
    (for-each print (numbers-in l))))

(define print-numbers4
  (lambda (l)
    (for ((item l))
      (when(number? item)
        (print item)))))

(define squared-numbers
  (lambda (l)
    (cond ((null? l) '())
          ((number? (car l))
           (cons (*(car l) (car l))
                 (squared-numbers (cdr l))))
          (else (squared-numbers (cdr l))))))

(define squared-odds-cubed-evens
  (lambda (l)
    (cond ((null? l) '())
          ((number? (car l))
           (if (odd?(car l))
               (cons (*(car l) (car l))
                     (squared-odds-cubed-evens (cdr l)))
               (cons (*(car l) (car l)(car l))
                     (squared-odds-cubed-evens (cdr l)))))
          (else (squared-odds-cubed-evens (cdr l))))))

(define squared-odds-cubed-evens2
  (lambda (l)
    (cond ((null? l) '())
          ((number? (car l))
           (cons (if (odd?(car l))
                     (*(car l) (car l))
                     (*(car l) (car l)(car l)))
                 (squared-odds-cubed-evens2 (cdr l))))
          (else (squared-odds-cubed-evens2 (cdr l))))))
               
(define print-numbers-nested
  (lambda (l)
    (cond ((null? l) (void))
          ((number? (car l))
           (print (car l))
           (print-numbers-nested (cdr l)))
          ((list? (car l))
           (print-numbers-nested (car l))
           (print-numbers-nested (cdr l)))
          (else
           (print-numbers-nested (cdr l))))))

(define mynest '(a 2 3 (h 3 4 (3 4 56 9) a (b) (2 3))))

;(print-numbers-nested mynest)

(define squared-numbers-nested
  (lambda (l)
    (cond ((null? l) '())
          ((number? (car l))
           (cons (*(car l) (car l))
                 (squared-numbers-nested (cdr l))))
          ((list? (car l))
           (cons (squared-numbers-nested (car l))
                   (squared-numbers-nested (cdr l))))
          (else (squared-numbers-nested (cdr l))))))

(squared-numbers-nested mynest)