1 ;; The first three lines of this file were inserted by DrScheme. They record metadata
2 ;; about the language level of this file in a form that our tools can easily process.
3 #reader(lib "htdp-intermediate-reader.ss" "lang")((modname |23.1|) (read-case-sensitive #t) (teachpacks ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp")))))
4 ;; make-even : N  ->  N[even]
5 ;; to compute the i-th even number
6 (define (make-even i)
7   (* 2 i))         	
8 
9 ;; make-odd : N  ->  N[odd]
10 ;; to compute the i-th odd number
11 (define (make-odd i)
12   (+ (* 2 i) 1))
13 
14 ;; series : N (N  ->  number)  ->  number
15 ;; to sum up the first n numbers in the sequence a-term,
16 (define (series n a-term)
17   (cond
18     [(= n 0) (a-term n)]
19     [else (+ (a-term n)
20 	     (series (- n 1) a-term))]))
21 
22 ;; series-even1 : N  ->  number
23 (define (series-even1 n)
24   (series n make-even))	 	
25 
26 ;; series-odd1 : N  ->  number
27 (define (series-odd1 n)
28   (series n make-odd))
29