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CS 1400
Chapter 10
10.1 Character Testing
• There are several functions that answer
questions about characters
• Each has one char parameter
• Each returns true or false
Character Testing
- require cctype header file?
FUNCTION MEANING
isalpha true if arg. is a letter, false otherwise isalnum true if arg. is a letter or digit, false otherwise isdigit true if arg. is a digit 0-9, false otherwise islower true if arg. is lowercase letter, false otherwise isprint true if arg. is a printable character, false otherwise ispunct true if arg. is a punctuation character, false otherwise isupper (^) true if arg. is an uppercase letter, false otherwise isspace true if arg. is a whitespace character, false otherwise
Example
10.2 Character Case Conversion
- Require cctype header file.?
- Functions: toupper: if char argument is lowercase letter, return uppercase equivalent; otherwise, return input unchanged char ch1 = 'H'; char ch2 = 'e'; char ch3 = '!'; char c1 = toupper(ch1); // assigns 'H' char c2 = toupper(ch2); // assigns 'E' char c3 = toupper(ch3); // assigns '!'
Character Case Conversion
- Functions: tolower: if char argument is uppercase letter, return lowercase equivalent; otherwise, return input unchanged char ch1 = 'H'; char ch2 = 'e'; char ch3 = '!'; char c1 = toupper(ch1); // assigns ‘h' char c2 = toupper(ch2); // assigns ‘e' char c3 = toupper(ch3); // assigns '!'
10.3 Review of the Internal
Storage of C-Strings
- C-string: sequence of characters stored in
adjacent memory locations and terminated by
NULL character
- String literal (string constant): sequence of
characters enclosed in double quotes " " :
"Hi there!"
H i t h e r e! \
Review of the Internal
Storage of C-Strings
- Array of chars can be used to define storage for string: const int SIZE = 20; char city[SIZE];
- Leave room for NULL at end
- Can enter a value using cin or >>
- Input is whitespace-terminated
- No check to see if enough space
- For input containing whitespace, and to control amount of input, use cin.getline()
- can write entire array using cout
cout<<city;
Review of the Internal Storage of
C-Strings
10.4 Library Functions for
Working with C-Strings
- These functions require c-strings as parameters (actually the address of a c-string.) This can be accomplished by - sending the name of an array holding a c-string - a char pointer (we'll learn about these later) - a string constant
- Some of these c-string functions lead to potential security hazards and have been deprecated.
- These will produce a warning in the Visual Studio environment
- Although the textbook uses the deprecated versions of these functions, we will use the newer, more secure versions
Library Functions for
Working with C-Strings
Functions:
- strlen(str): returns length of C-string str char city[SIZE] = "Missoula"; cout << strlen(city); // prints 8
- strcat_s(str1, str2): appends str2 to the end of str const int SIZE = 100; char location[SIZE] = "Missoula, "; char state[3] = "MT"; strcat_s(location, state); // location now has "Missoula, MT"
Library Functions for
Working with C-Strings
Functions:
- strcpy_s(str1, str2): copies str2 to
str
const int SIZE = 100; char fname[SIZE] = "Maureen", name[SIZE]; strcpy_s(name,fname);
Input into a string Object
• Use getline function to put a line of
input, possibly including spaces, into a
string:
string address;
cout << "Enter your address: ";
getline(cin,address);
string Comparison
- Can use relational operators directly to compare string objects: string str1 = "George", str2 = "Georgia"; if (str1 < str2) cout << str1 << " is less than " << str2;
- Comparison is performed similar to strcmp function. Result is true or false
Example strings
• It also works with the + operator
• The + operator performs concatenation:
fullName=first + " " + last;
• You can use the array operator [] to
access a single a character.
title="Ice Age";
cout<<title[4];//prints A
Other Definitions of C++ strings
- There are multiple ways to define a string
Definition Meaning string name; defines an empty string object string myname("Chris"); (^) defines a string and initializes it string yourname(myname);
defines a string and initializes it string aname(myname, 3);
defines a string and initializes it with first 3 characters of myname string verb(myname,3,2);
defines a string and initializes it with 2 characters from myname starting at position 3 string noname('A', 5); (^) defines string and initializes it to 5 'A's
string Operators
OPERATOR MEANING
extracts characters from stream up to whitespace, insert into string << inserts string into stream = assigns string on right to string object on left += (^) appends string on right to end of contents on left
- (^) concatenates two strings [] (^) references character in string using array notation
, >=, <, <=, ==, !=
relational operators for string comparison. Return true or false
string Operators
string word1, phrase; string word2 = " Dog"; cin >> word1; // user enters "Hot Tamale" // word1 has "Hot" phrase = word1 + word2; // phrase has // "Hot Dog" phrase += " on a bun"; for (int i = 0; i < 16; i++) cout << phrase[i]; // displays // "Hot Dog on a bun"
string Member Functions
- Are behind many overloaded operators
- Categories:
- assignment: assign, copy, data
- modification: append, clear, erase, insert, replace, swap
- space management: capacity, empty, length, resize, size
- substrings: find, substr
- comparison: compare
- See Table 10-7 for a list of functions
string Member Functions
string word1, word2, phrase; cin >> word1; // word1 is "Hot" word2.assign(" Dog"); phrase.append(word1); phrase.append(word2); // phrase has "Hot Dog" phrase.append(" with mustard relish", 13); // phrase has "Hot Dog with mustard" phrase.insert(8, "on a bun "); cout << phrase << endl; // displays // "Hot Dog on a bun with mustard"
Arrays of strings
• These are 1-D arrays:
string titles[size];
