1. Jeff West - Quiz Section 6
CSE 143 Section AD
Quiz Section 6
7/5/2001
Jeff West - Quiz Section 6

2. Jeff West - Quiz Section 6
Announcements
If you are not yet officially registered for this course, please make sure to talk to me after class
There will be two debugger tutorials next week… one on Tuesday at 3:30 and the other TBA
7/5/2001
Jeff West - Quiz Section 6

3. String “find” Member Function
If you’ve #included string, one function you can take advantage of is “find”:
string s;
s.find(“sometext”);
will return the subscript position where you can find “sometext” (in the 0, 1, … , n number system)
The function will return the constant string::npos if “sometext” is no where to be found!
Create a program which will keep prompting a user for a sentence and tell the user where “hi” was first found in the sentence until the user enters a sentence which does not include the word “hi”, at which point the program will exit.
7/5/2001
Jeff West - Quiz Section 6

4. Jeff West - Quiz Section 6
A possible solution…
#include<iostream>
#include<string>
using namespace std;
void main() {
string userEntry; // user sentence
int pos; // position of word
cout << “Enter a sentence: “;
cin >> userEntry;
pos = userEntry.find(“hi”);
while(pos != string::npos) {
cout << “hi can be found at position “ << pos << “.\n”; }
7/5/2001
Jeff West - Quiz Section 6

5. How to Implement a Menu…
Switch Statements and “Interpreter” functions – Example, HW 3 from Last Quarter
“Clean” typedef example… a little advanced so if you don’t understand it, don’t use it and don’t worry about it …
7/5/2001
Jeff West - Quiz Section 6

6. A Switch Statement Menu
// options available to the user in the main menu
enum MainMenuOption {
ReadFile,
SearchTitle,
...
Quit };
// show main menu and handle the user's selections, maintaining the database.
int main() {
bool quit = false; // set to true when the user asks to quit.
while( !quit ) { // exits directly using "return" if user quits
MainMenuOption option = doMainMenu();
switch( option ) {
case ReadFile:
... Call other functions, etc.
break;
7/5/2001
Jeff West - Quiz Section 6

7. case SearchPerformer:
... Call other functions, etc.
break;
case Quit:
quit = true;
default:
// shouldn't get here (unknown option)
assert( false ); }
cout << "Good bye!" << endl;
return 0;

8. Jeff West - Quiz Section 6
MainMenuOption()
// display the main menu and allow user to select an option from it.
// returns the selected option.
MainMenuOption doMainMenu() {
string entry; // user's entry at menu prompt
while( true ) { // loop exited using "return"
cout << "Please choose from the following options:" << endl;
cout << "(R)ead a file into the database" << endl; …
cout << "(Q)uit." << endl;
cin >> entry;
if( entry.length() == 1 ) {
switch( entry[ 0 ] ) {
case 'R':
case 'r': return ReadFile;
case 'Q':
case 'q': return Quit; }
7/5/2001
Jeff West - Quiz Section 6

9. Jeff West - Quiz Section 6
A Typedef Menu(1)…
In Header File:
// first test function
int func1() { return 1; }
// second test function
int func2() { return 2; }
// third test function
int func3() { return 3; }
// define a "command" type to lookup function to be called
typedef int(*cmd_ptr)();
7/5/2001
Jeff West - Quiz Section 6

10. Jeff West - Quiz Section 6
A Typedef Menu(2)…
In .cpp file:
#include<iostream>
using namespace std;
#include"functions.h"
int main() {
int cmd; // stores the command requested by the user
cmd_ptr commands[] = { func1, func2, func3 }; // array of functions to be called
while(true) {
cin >> cmd;
cout << (*commands[cmd-1])(); }
return 0;
7/5/2001
Jeff West - Quiz Section 6

11. A Typedef Menu in a Class(1)
class Functions {
public:
// first test function
int func1() { return 1; }
// second test function
int func2() { return 2; }
// third test function
int func3() { return 3; } };
// define a "command" type to lookup function to be called
typedef int(Functions::*cmd_ptr)();
7/5/2001
Jeff West - Quiz Section 6

12. A Typdef Menu in a Class(2)
#include<iostream>
using namespace std;
#include"functions.h"
int main() {
Functions tester; // tests the function lookup table
int cmd; // stores the command requested by the user
cmd_ptr commands[] = { &Functions::func1, &Functions::func2, \
&Functions::func3 }; // array of functions to be called
// an infinite loop that assumes it is okay to go on forever
while(true) {
cout << "Enter a number for me to print: ";
cin >> cmd;
cout << (tester.*commands[cmd-1]) () << '\n'; }
return 0;
7/5/2001
Jeff West - Quiz Section 6