;;; File:
;;;   higher-order.scm
;;; Authors:
;;;   Samuel A. Rebelsky
;;;   The Students of CSC151.02 2003F
;;; Summary:
;;;   A variety of higher-order procedures and related stuff.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Examples: Similar Procedures ;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; All the values in a list greater than 100
(define big-numbers
  (lambda (lst)
    (cond
      ((null? lst) null)
      ((< 100 (car lst)) (cons (car lst) (big-numbers (cdr lst))))
      (else (big-numbers (cdr lst))))))

(define all-numbers
  (lambda (lst)
    (cond
      ((null? lst) null)
      ((number? (car lst)) (cons (car lst) (all-numbers (cdr lst))))
      (else (all-numbers (cdr lst))))))


(define safe-big-numbers
  (lambda (lst)
    (cond
      ((null? lst) null)
      ((not (real? (car lst))) (error 'big-numbers "Ugh!"))
      ((< 100 (car lst)) (cons (car lst) (big-numbers (cdr lst))))
      (else (big-numbers (cdr lst))))))
      

(define select
  (lambda (good? lst)
    (cond 
      ((null? lst) null)
      ((good? (car lst)) (cons (car lst) (select good? (cdr lst))))
      (else (select good? (cdr lst))))))

(define get-numbers
  (lambda (lst)
    (select number? lst)))


(define bigstuff
  (lambda (lst)
    (let ((big? (lambda (val) (> val 100))))
      (select big? lst))))

(define all-real?
  (lambda (lst)
    (or (null? lst) 
        (and (real? (car lst))
             (all-real? (cdr lst))))))

(define all
  (lambda (good? lst)
    (or (null? lst)
        (and (good? (car lst))
             (all good? (cdr lst))))))
    
(define all-small?
  (lambda (lst)
    (all (lambda (x) (< x 10)) lst)))