Object-Oriented Programming with C++ Strings: Lecture 22 - Prof. Jeffrey A. Miller, Study notes of Engineering

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CSE294B

Object-Oriented C++ Programming for Engineers

Lecture

Jeffrey Miller, Ph.D.

string

The string type in C++ is actually a typedef of a template classcalled basic_string

The template definition is in the std namespace

This allows us to create a string object as such:

string text(“hello”);

The above line will call the basic_string constructor, andpass in the char* “hello”

We can also instantiate a string with a value as follows:

string text = “hello”;

The assignment operator is overloaded in the basic_string classto call the constructor

NOTE: There isn’t actually a class called “string” in C++,though many sources reference the “string” class when referringto the “basic_string” class

I will use this notation throughout this lecture

string Example

#include

#include

using namespace std;

void main() {

string s1("hello");

string s2 = "world";

string s3;

s3 = s1;

// s3.assign(s1);

s3 += " " + s2;

// s3.append(" " + s2);

cout << "s1 = " << s1 << endl;

cout << "s2 = " << s2 << endl;

cout << "s3 = " << s3 << endl;

Overloaded string Operators

The string class has overloaded the ==, !=, <, >, >=, <= operators to operate onthe value of the strings instead of the reference of the string (as in C) 1 string s1("hello"); 2 string s

"world"; 3 string s3, s4; 4 5 s

s

s2; 6

appends the substring from s from index

to the number 7

of characters specified by the third parameter 8

NOTE:

the third parameter is not an index, but a length 9 s4.append(s3,

if (s

s4)

cout

s

s

endl; 13

cout

"s

s

endl; 16 cout

"s

s

endl; 17 cout

"s

s

endl; 18 cout

"s

s

endl;

swap Function

The string class has a swap function thatdoes exactly that

string s1("hello");

string s2 = "world";

s1.swap(s2);

cout

"s

s

endl;

cout

"s

s

endl;

Length vs Capacity of a string

The size or length of a string is the number of characters currently stored in the string - The capacity of a string is the number of characters that can be stored in the string withouthaving to allocate more memory - The max_size of a string is the maximum number of characters allowed in a string

void print_stats(string s) {

cout << "s = " << s << endl;

cout << "s.length() = " << s.length() << endl;

cout << "s.size() = " << s.size() << endl;

cout << "s.capacity() = " << s.capacity() << endl;

cout << "s.max_size() = " << s.max_size() << endl;

void main() {

string s1("hello");

print_stats(s1);

s1 = "hello everyone in the world";

print_stats(s1);

Program

Write a program that reads two strings from the user, thenputs the characters in alphabetical order using the stringfunctions we just discussed.

Homework

Homework #6 is posted!