04-C++-Strings

04-C++-Strings - CS106X Winter 2010 Handout 04 C+ Strings...

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CS106X Handout 04 Winter 2010 January 6 th , 2010 C++ Strings Original handout written by Neal Kanodia, with help from Steve Jacobson. C++ Strings One of the most useful data types supplied in the C++ libraries is the string. A string is a variable that stores a sequence of letters or other characters, such as " Hello " or " May 10th is my birthday !" . Just like the other data types, to create a string we first declare it, then we can store a value in it. string testString; testString = "This is a string."; We can combine these two statements into one line: string testString = "This is a string."; Often, we use strings as output, and cout works exactly like one would expect: cout << testString << endl; will print the same result as cout << "This is a string." << endl; In order to use the string data type, the C++ string header <string> must be included at the top of the program. Also, you’ll need to include genlib.h to make the short name string visible instead of requiring the cumbersome std::string . (As a side note, std is a C++ namespace for many pieces of functionality that are provided in standard C++ libraries. For the purposes of this class, you won't need to know about namespaces.) Thus, you would have the following #include 's in your program in order to use the string type. #include <string> #include "genlib.h" A string is basically a sequence of characters. Basic Operations Let’s go into specifics about the string manipulations you’ll be doing the most. Counting the number of characters in a string. The length method returns the number of characters in a string, including spaces and punctuation. Like many of the string operations, length is a member function , and we invoke member functions using dot notation . The string that is the receiver is to the left of the dot, the member function we are
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2 invoking is to the right, (e.g. str.length() ). In such an expression, we are requesting the length from the variable str . example program: #include <string> #include <iostream> #include "genlib.h" int main() { string small, large; small = "I am short"; large = "I, friend, am a long and elaborate string indeed"; cout << "The short string is " << small.length() << " characters." << endl; cout << The long string is " << large.length() << " characters." << endl; return 0; } output: The short string is 10 characters. The long string is 48 characters. Accessing individual characters. Using square brackets, you can access individual characters within a string, similar to as if the string were an array. Just as with array access, positions are numbered starting from 0, and the last position is (length - 1). Using square brackets, you can both read the character at a position and assign to that position. example program:
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This note was uploaded on 03/07/2010 for the course CS 201 taught by Professor Selimaksoy during the Spring '09 term at Bilkent University.

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04-C++-Strings - CS106X Winter 2010 Handout 04 C+ Strings...

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