1. Strings

2. Using strings as abstract value A string is a sequence of characters e.g. “Hello, World!” Early version of C++ followed the older C language (A string is an array of character, a little support for manipulating strings.) New version of C++, introducing a string class. We can use string as a primitive data type.

3. Using strings as abstract value Declaration const string ALPHABET = “ABCDEFGHIJKLMNOPQRSTUVWXYZ”;

4. Using strings as abstract value int main() { string name; cout << "Enter your name: "; cin >> name; cout << "Hello, " << name << "!" << endl; return 0; } Enter your name: Wiboon Hello, Wiboon! Enter your name: Wiboon Promphanich Hello, Wiboon! The operator >> stops when it hits the first whitespace character. (blank, tab, end-of-line)

5. #include using namespace std; int main() { string name; cout << "Enter your name: "; getline(cin, name); cout << "Hello, " << name << "!" << endl; return 0; }

6. int main() { string name; cout << "Enter your name: "; getline(cin, name); cout << "Hello, " << name << "!" << endl; return 0; } Enter your name: Wiboon Hello, Wiboon! Enter your name: Wiboon Promphanich Hello, Wiboon Promphanich!

7. #include #include "simpio.h" using namespace std; int main() { string name = getLine("Enter your full name: "); cout << "Hello, " << name << "!" << endl; return 0; }

8. String operations Class Object Instance Method Free function Sender Receiver Messages

9. String operations string str = “abc”; int nChars = str.length(); str += “abc”; if (str == “quit”) … Relational operators using lexicographic order, defined by ASCII code.

10. String operations hello,world 01234567891011

11. Selecting character from a string str[0] no range-checking str.at(0)range checking string index and length in string using type size_t, is automatically defined when you include the header file. str = str1;

12. String assignment and extracting str2 = str1;overwrites content of str2 str.substr(1,3);return “ell” str.substr(7);return “world” string secondHalf(string str) { return str.substr(str.length() / 2); }

13. Searching within a string str.find(‘o’)return 4 str.find(‘o’,5)return 8 str.find(‘x’)return string::npos (defined in the string class)

14. Iterating in a string for (int i = 0; i < str.length(); i++) {... body of loop that manipulates str[i]... } int countSpaces(string str) { int nSpaces = 0; for (int i = 0; i < str.length(); i++) { if (str[i] == ' ') nSpaces++; } return nSpaces; }

15. Iterating in a string for (int i = str.length() - 1; i >= 0; i--) for (int i = 0; i < str.length(); i++)

16. Iterating in a string bool startsWith(string str, string prefix) { if (str.length() < prefix.length()) return false; for (int i = 0; i < prefix.length(); i++) { if (str[i] != prefix[i]) return false; } return true; }

17. A string concatenation string str = ""; for (whatever loop header line fits the application) { str += the next substring or character; } string repeatChar(int n, char ch) { string str = ""; for (int i = 0; i < n; i++) { str += ch; } return str; } cout << repeatChar(72, '-') << endl;

18. A string concatenation string reverse(string str) { string rev = ""; for (int i = str.length() - 1; i >= 0; i--) { rev += str[i]; } return rev; }

19. Methods in library String operators str1 + str2 str1 += str2 str1 == str2 str1 != str2 st1 < str2 str1 <= str2 st1 > str2 str1 >= str2 str[k] Receiver string unchanged str.length() str.at(k) str.substr(pos,k) str.compare(str2) str.find(pattern, pos)

20. Methods in library Modify receiver string str.erase(pos, n) str.insert(pos, str2) str.replace(pos, n, str2) Creating C++ and C-style string string(carray) string(n, ch) str.c_str()

21. Functions in library Predicate functions isalpha(ch) isupper(ch) islower(ch) isdigit(ch) isxdigit(ch) isalnum(ch) ispunct(ch) isspace(ch) isprint(ch) Case conversion toupper(ch) tolower(ch)

22. bool isDigitString(string str) { if (str.length() == 0) return false; for (int i = 0; i < str.length(); i++) { if (!isdigit(str[i])) return false; } return true; }

23. bool equalsIgnoreCase(string s1, string s2) { if (s1.length() != s2.length()) return false; for (int i = 0; i < s1.length(); i++) { if (tolower(s1[i]) != tolower(s2[i])) return false; } return true; }

24. Modifying the contents of a string void toUpperCaseInPlace(string & str) { for (int i = 0; i < str.length(); i++) { str[i] = toupper(str[i]); }

25. Modifying the contents of a string string toUpperCase(string str) { string result = ""; for (int i = 0; i < str.length(); i++) { result += toupper(str[i]); } return result; }

26. Modifying the contents of a string string str = "hello, world"; string str = "hello" + ", " + "world"; (Bug) string str = string("hello") + ", " + "world";

27. Palindrome bool isPalindrome(string str) { int n = str.length(); for (int i = 0; i < n / 2; i++) { if (str[i] != str[n - i - 1]) return false; } return true; }

28. Palindrome bool isPalindrome(string str) { return str == reverse(str); } The first implementation is more efficient. The second is better for for new programmer.

29. The strlib.h library integerToString(n) stringToInteger(str) realToString(d) stringToReal(str) toUpperCase(str) toLowerCase(str) equalsIgnoreCase(s1,s2) startsWith(str, prefix) endsWith(str, suffix) trim(str)