C++ STRINGS string is part of the Standard C++ Library Finally we get to the STL string class. This is not the C type character array that we have seen so far (even though internally it may use an array). This string class provides a lot more usability and protection. An example (using command line arguments will be shown after the preliminary coverage)

#include <string> Provides access to the standard string library. Look in includes for reference /usr/include/g++-3 (Red Hat Linux 8.0)

string name; Instantiates a local variable (named object) of type string. Can be anywhere before it's used. Gains access to the interface, (the member functions (methods) or operations of the string type. This definition uses the default constructor and generates a null string. Scope is only for this function (main) and is destroyed when leaving the scope.

cin >> name; Read from the standard input into the data area of name. First it skips any whitespace characters (space, tab, backspace, or end of the line). Next it reads any characters into name until it encounters another whitespace character or end-of-file. The value of the expression is cin. Tries to flush properly to display previous couts.

const string greeting = "Hello, " + name + "!"; const promises that we will never change this variable again. const definitions MUST be initialized when defined. This definition can use the values of previous variables as it does here. + is a concatenation operator within the string object. ("x"+name, name+"x", name+name, but NOT "x"+"x"); Example of overloading the + operator.

const string spaces(greeting.size( ), ' '); Another instantiation of a object of type string. This object is called spaces. In this example, a different constructor is called. (num, character) returns num characters. greeting.size() is a member function of the greeting object which returns an integer number for the length of the string stored in greeting. Result is a set of spaces the same size as greeting.

CHARACTER LITERALS In the previous constructor (num character) we used the character literal ' ' for a single character that is a blank. Distinct from the string literal " ". The type of ' ' is char. The type of " " is an array of const char with one more element than the number of characters in the literal (the '\0' null character).

DETAILS char : built-in type that holds ordinary characters defined by the implementation. wchar_t: built-in type that holds "wide characters" which are big enough to hold characters for languages such as Japanese.

STRING CONSTRUCTORS string s; creates the empty string s string s(str); creates a string as a copy of the existing string str. string s(str, stridx); creates a string s that is initialized by the characters of string str starting with index stridx. string(str, stridx, strlen); creates a string s that is initialized by, at most, strlen characters of string str starting with index stridx.

STRING CONSTRUCTORS (cont.) string s(cstr); creates a string s that is initialized by the C-string cstr. string s(chars, chars_len); creates a string s that is initialized by chars_len characters of the character array chars. string s(num c); creates a string that has num occurrences of character c. string s(beg,end); creates a string that is initialized by all characters of the range [beg,end].

STRING DESTRUCTOR s.~string( ); destroys all characters and frees the memory.

STRING MEMBER FUNCTIONS (METHODS) =,assign( ) Assign a new value swap( ) Swaps values between two strings +=, append( ), push_back( ) Appends characters insert( ) Inserts characters erase( ) Erase characters clear( ) Remove all characters (makes it empty) resize( ) Changes the number of characters (deletes or appends characters at the end)

STRING MEMBER FUNCTIONS (cont.) replace( ) Replaces characters + Concatenates strings ==, !=, <, <=, >, >=, compare( ) Compare strings size( ), length( ) Return the number of characters max_size( ) Returns the maximum possible number of characters empty( ) Returns whether the string is empty capacity( ) Returns the number of characters that can be held without reallocation.

STRING MEMBER FUNCTIONS (cont.) reserve( ) Reserves memory for a certain number of characters [ ], at( ) Access a character >>, getline( ) Read the value from a stream << Writes the value to a stream copy( ) Copies or writes the contents to a C-string c_str( ) Returns the value as C-string

STRING MEMBER FUNCTIONS (cont.) data( ) Returns the value as character array substr( ) Returns a certain substring find functions Search for a certain substring or character begin( ), end( ) Provide normal iterator support rbegin( ), rend( ) Provide reverse iterator support get_allocator( ) Returns the allocator AND, there are even more (check the reference manual for all the details) Practice: inclass strings