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-advanced-reader.ss" "lang")((modname |35.4|) (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 #t #t none #f ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp")))))
4 ;An address-book (ab) is either
5 ;1. empty or
6 ;2. (cons s (cons n ab)) [(list (list s n)
7 ;                               ab)]
8 ;where s is a symbol, n is a number, and ab is an address-book.
9 
10 (define my-book empty)
11 
12 add-to-address-book : symbol number -> void
13 
14 (define (add-to-address-book name phone)
15   (set! my-book (cons (list name phone) my-book)))