CSC134 OOP in C++ - ISO C++ String Class Methods

ISO C++ String Class Methods

ISO C++ has a string class in the Standard Library. This handout is not a complete listing of the facilities of the string class; it describes the most commonly used member functions. Information on how to create and initialize strings can be found in the ISO C++ String Class handout. Remember, that the first character in a string is in position 0.

int string::length() const;

The length member function returns the length of the invoking object. For example:

       string saying("all's well that ends well");
       cout << "The length of saying is "
                                << saying.length() << endl;

The output is:

       The length of saying is 25

char string::at(int) const;

The at member function returns the character in the position of the invoking object given by the parm. For example:

       string saying("all's well that ends well");
       cout << "The seventh character is "
                                << saying.at(6) << endl;

The output is:

       The seventh character is w

string& string::insert(int pos, const string& str);

The insert member function has two parms: the first is an int, and the second is a string. insert adds the second parm into the invoking object starting in the position given by the first parm. For example:

       string saying("all's well that ends well");
       string addition("**hi**");
       saying.insert12,(addition);
       saying.insert(1,"more");
       cout << saying << endl;

The output is:

       amorell's well t**hi**hat ends well

string& string::erase(int pos, int n=npos);

The erase member function has two parms; the first is an int for the starting position, the second is an int for the number of characters to delete. erase deletes characters from the invoking object. The characters removed start in the position given by the first parm. The number of characters removed is given by the second parm. If the second parm is not specified, all characters from the starting position to the end of the string are deleted, since the special constant npos indicates that the rest of the characters in the string should be deleted. For example:

       string saying("all's well that ends well");
       saying.erase(2,6);
       cout << saying << endl;
       saying.erase(16);
       cout << saying << endl;

The output is:

       alll that ends well
       alll that ends w

string string::substr (int pos, int n) const;

The substr member function has two parms; the first in an int for the starting position, the second is an int for the number of characters to return. substr returns a substring from the invoking object. The substring starts with the character in the position given by the first parm, and has length given by the second parm. The invoking object is unchanged. For example:

       string saying("all's well that ends well");
       string sub = saying.substr(4,10);
       cout << sub << endl;

The output is:

       s well tha

int find (const string& str, int pos=0) const; int find (char ch, int pos=0) const;

The find member function searches the invoking object for the string or character given by the first parm, and returns the position where the first parm is found. If the second parm is not specified, the search starts at the beginning of the string. If the second parm is specified, the search starts in the position given by the second parm. For example:

       string saying("all's well that ends well");
       string search("well");
       int loc = saying.find(search);
       cout << "well is found in position " << loc << endl;
       loc = saying.find(search,loc+1)
       cout << "well is found again in position "
                                      << loc << endl;

The output is:

       well is found in position 6
       well is found again in position 21