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 17.6.6) (read-case-sensitive #t) (teachpacks ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "dir.ss" "teachpack" "htdp") (lib "hangman.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "dir.ss" "teachpack" "htdp") (lib "hangman.ss" "teachpack" "htdp")))))
4 A list-of-symbols is either
5 1. empty or
6 2. (cons s los)
7 where s is a one-letter symbol and los is a list-of-symbols.
8 
9 DNAprefix : list-of-symbols list-of-symbols -> boolean
10 Given pattern and search-string, determine if pattern occurs in search-string.
11 
12 (define (DNAprefix pattern search-string)
13   (