CS111 Lab Strings and classes

Instructor: Michael Gordon

What are classes?

C++ was originally called “C with classes”

A class can be thought of as new type of

variable that you can create.

Just like functions are new operations you

can write, classes are new variables

We’ve used one kind of class already: the

string class

string and its functions are built into C++.

Strings

The internal construction of a string is

really an array of characters.

To find the length of a string s we can use

the functions .length() or .size

int x = s.length(); gives x the value of the

size of the string s.

To “concatenate” two strings s1 and s2:

string s3 = s1+s2;

String examples string first, last, name;

cout<<"Enter your first name:";

cin>>first;

cout<<"Enter your last name:";

cin>>last;

cout<<"Hi, "+first+" "+last; //concat

getline()

cin reads the typed string only until the first

whitespace.

If you want the whole string including

those whitespaces, you can use:

getline(cin, stringname);

cout<<“Enter your name:”;

getline(cin, fullname);

Use fullname instead of first and last.

“dot” functions

With strings we start dealing with a new

kind of function call. These functions

operate on a specific “object” (an

instance of a class).

We write the object name (e.g. the

variable name of the string) followed by

period and the function call (no space

before or after the period).

More functions

s1.find(string s2) – returns the index of the

beginning of s2 in s1.

s1 = “hello”;

s1.find(“lo”) – returns 3

s1.insert(int i, string s2) – inserts s2 into s1 at

index I

s1.at(int i) – returns the character at index

i in string s1