1. C++ Programming:. Program Design Including
C++ Programming: Program Design Including Data Structures, Second Edition
Chapter 8: User-Defined Simple Data Types, Namespaces, and the string Type

2. Objectives
In this chapter you will:
Learn how to create and manipulate your own simple data type — called the enumeration type
Become aware of the typedef statement
Learn about the namespace mechanism
Explore the string data type, and learn how to use the various string functions to manipulate strings
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

3. Enumeration Type
Data type - a set of values together with a set of operations on those values
To define a new simple data type, called enumeration type, we need three things:
A name for the data type
A set of values for the data type
A set of operations on the values
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

4. Enumeration Type (continued)
The syntax for enumeration type is:
enum typeName{value1, value2, ...};
value1, value2, … are identifiers called enumerators
value1 < value2 < value3 <...
A new simple data type can be defined by specifying its name and the values, but not the operations
The values must be identifiers
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

5. Enumeration Type is an ordered set of values
If a value has been used in one enumeration type
It cannot be used by another in the same block
enum mathStudents{John, Bill, Lisa};
enum compStudents {Susan, John, william};
John is not allowed in the 2nd enum type
The same rules apply to enumeration types declared outside of any blocks
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

6. Enumeration Types
C++ allows creation of a new simple type by listing (enumerating) all the ordered values in the domain of the type
EXAMPLE
Below JAN < FEB < MAR < APR , and so on
enum MonthType { JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC } ;
name of new type
list of all possible values of this new type
expanded by J. Goetz, 2004

7. Examples
The following are illegal enumeration types because none of the values is an identifier:
enum grades{'A', 'B', 'C', 'D', 'F'};
enum places{1st, 2nd, 3rd, 4th};
The following are legal enumeration types:
enum grades{A, B, C, D, F};
enum places{first, second, third, fourth};
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

8. Declaring Variables The syntax for declaring variables is:
dataType identifier, identifier,...;
The following statement defines an enumeration type sports
enum sports{basketball, football, hockey,
baseball, soccer, volleyball};
The following statement declares variables of the type sports.
sports popularSport, mySport;
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

9. Assignment The statement: popularSport = football;
stores the word football into popularSport
mySport = popularSport;
copies the contents of the variable popularSport into mySport
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

10. Declaring enum Type Variables
enum MonthType { JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC } ;
MonthType thisMonth; // declares 2 variables
MonthType lastMonth; // of type MonthType
lastMonth = OCT ; // assigns values
thisMonth = NOV ; // to these variables .
lastMonth = thisMonth ;
thisMonth = DEC ; 10
expanded by J. Goetz, 2004

11. Storage of enum Type Variables
stored as stored as stored as stored as 3 etc.
enum MonthType { JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC } ;
stored as 11
expanded by J. Goetz, 2004

12. Operations No arithmetic operation is allowed on enumeration types
The following statements are illegal;
mySport = popularSport + 2; //illegal
popularSport = football + soccer; //illegal
popularSport = popularSport * 2; // illegal
The increment and decrement operations are not allowed on enumeration types
popularSport++; //illegal
popularSport--; //illegal
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

13. C++ Simple Data Types simple types integral floating
char short int long bool enum float double long double
unsigned
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

14. More about enum Type
Stream I/O ( using the insertion << and extraction >> operators ) is not defined for enumeration types. Instead, functions can be written for this purpose.
Input and output are defined only for built-in data types such as int, char, double
The enumeration type can be neither input nor output (directly)
Comparison of enum type values is defined using the 6 relational operators ( < , <= , > , >= , == , != ).
Enumeration type can be used in a Switch statement for the switch expression and the case labels.
An enum type can be the return type of a value-returning function in C++.
expanded by J. Goetz, 2004

15. Operations and Input/Output
Because an enumeration is an ordered set of values
We can use relational operators with them
The cast operator can be used to increment, decrement, and compare values
popularSport = static_cast <sports> (popularSport +1);
popularSport++; //illegal
football <= soccer // is true
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

16. switch ( thisMonth ) // using enum type switch expression { case JAN :
MonthType thisMonth;
switch ( thisMonth ) // using enum type switch expression {
case JAN :
case FEB :
case MAR : cout << “Winter quarter” ;
break ;
case APR :
case MAY :
case JUN : cout << “Spring quarter” ;
case JUL :
case AUG :
case SEP : cout << “Summer quarter” ;
case OCT :
case NOV :
case DEC : cout << “Fall quarter” ; } 16
expanded by J. Goetz, 2004

17. Functions and Enumeration Types
Enumeration type can be passed as parameters to functions either by value or by reference
A function can return a value of the enumeration type
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

18. Using enum type Control Variable with for Loop
enum MonthType { JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC } ;
void WriteOutName ( /* in */ MonthType ) ; // prototype .
MonthType month ;
for (month = JAN ; month <= DEC ; month = static_cast <MonthType> (month + 1 ) )
{ // requires use of type cast to increment
WriteOutName ( month ) ; // function call to perform output } 18
expanded by J. Goetz, 2004

19. void WriteOutName ( /* in */ MonthType month )
// Prints out calendar name corresponding to month
// Precondition: month is assigned
// Postcondition: calendar name for month has been written out
{ switch ( month ) {
case JAN : cout << “ January ” ; break ;
case FEB : cout << “ February ” ; break ;
case MAR : cout << “ March ” ; break ;
case APR : cout << “ April ” ; break ;
case MAY : cout << “ May ” ; break ;
case JUN : cout << “ June ” ; break ;
case JUL : cout << “ July ” ; break ;
case AUG : cout << “ August ” ; break ;
case SEP : cout << “ September ” ; break ;
case OCT : cout << “ October ” ; break ;
case NOV : cout << “ November ” ; break ;
case DEC : cout << “ December ” ; break ; } 19
expanded by J. Goetz, 2004

20. Function with enum type Return Value
enum SchoolType { PRE_SCHOOL, ELEM_SCHOOL, MIDDLE_SCHOOL, HIGH_SCHOOL, COLLEGE } ; .
SchoolType GetSchoolData ( void )
// Obtains information from keyboard to determine school level
// Postcondition: Function value == personal school level {
SchoolType schoolLevel ;
int age ;
int lastGrade ;
cout << “Enter age : “ ; // prompt for information
cin >> age ; 20
expanded by J. Goetz, 2004

21. schoolLevel = PRE_SCHOOL ; else
if ( age < 6 )
schoolLevel = PRE_SCHOOL ;
else
{ cout << “Enter last grade completed in school : “ ;
cin >> lastGrade;
if ( lastGrade < 5 )
schoolLevel = ELEM_SCHOOL ;
else if ( lastGrade < 8 )
schoolLevel = MIDDLE_SCHOOL ;
else if ( lastGrade < 12 )
schoolLevel = HIGH_SCHOOL ;
schoolLevel = COLLEGE ; }
return schoolLevel ; // return enum type value 21
expanded by J. Goetz, 2004

22. Multifile C++ Programs
C++ programs often consist of several different files with extensions such as .h and .cpp
related typedef statements, const values, enum type declarations, and similar items are often placed in user-written header files
by using the #include preprocessor directive the contents of these header files are inserted into any program file that uses them
expanded by J. Goetz, 2004

23. Inserting Header Files
#include <iostream> // iostream
#include “school.h”
int main ( )
{ enum SchoolType
{ PRE_SCHOOL,
ELEM_SCHOOL, MIDDLE_SCHOOL,
HIGH_SCHOOL, COLLEGE } ; }
expanded by J. Goetz, 2004

24. Anonymous Data Types
Anonymous - a data type in which values are directly specified in the variable declaration with no type name, for example:
enum {basketball, football, baseball} mysport;
Creating an anonymous type has drawbacks
We cannot pass an anonymous type as a parameter to a function
use them with care !!!
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

25. Anonymous Data Types
A function cannot return a value of an anonymous type
Values used in one can be used in another, but they are treated differently
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

26. typedef Statement
You can create synonyms or aliases to a previously defined data type by using the typedef statement
The syntax of the typedef statement is:
typedef existingTypeName newTypeName;
typedef does not create any new data types
typedef creates an alias to an existing data type
typedef creates an additional name for an already existing data type
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

27. typedef statement
before bool type became part of ISO-ANSI C++, a Boolean type was simulated this way
typedef int Boolean; // new data type Boolean
const Boolean true = 1 ;
const Boolean false = 0 ; .
Boolean dataOK ;
dataOK = true ;
expanded by J. Goetz, 2004

28. ANSI/ISO Standard C++
ANSI/ISO standard C++ was officially approved in July 1998
Most of the recent compilers are also compatible with ANSI/ISO standard C++
this book focus
For the most part, standard C++ and ANSI/ISO standard C++ are the same, but
ANSI/ISO Standard C++ has some features not available in Standard C++
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

29. Namespaces
When a header file, such as iostream, is included in a program
Global identifiers in the header file also become global identifiers in the program
If a global identifier in a program has the same name as one of the global identifiers in the header file
The compiler will generate a syntax error (such as identifier redefined)
The same problem can occur if a program uses third party libraries
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

30. Namespaces (continued)
To overcome this problem, third party vendors begin their global identifiers with a special symbol
Because compiler vendors begin their global identifier with _ (underscore)
To avoid linking errors, do not begin identifiers in your program with _
ANSI/ISO standard C++ attempts to solve this problem of overlapping global identifier names with the namespace mechanism
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

31. Syntax: namespace The syntax of the statement namespace is:
namespace namespace_name {
members }
where a member is usually
a variable declaration,
a named constant, e.g. const double rate = 7.50;
a function, e.g. void printResult();
or another namespace
namespace globalType // e.g.
const double rate = 7.50;
void printResult();
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

32. Accessing a namespace Member
The scope of a namespace member is local to the namespace
Usually two ways a namespace member can be accessed outside the namespace
One way is to use the syntax:
namespace_name::identifier
To access the member rate of the namespace globalType, the following statement is required:
globalType::rate
To access the function printResult, the following statement is required:
globalType::printResult();
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

33. Accessing a namespace Member
2. To simplify the accessing of all namespace members:
using namespace namespace_name;
e.g. using namespace globalType;
using namespace std;
3. To simplify the accessing of a specific namespace member:
using namespace_name::identifier;
e.g. using globalType::rate;
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

34. The using Statement After the using statement
Not necessary to precede the namespace_name :: before the namespace member
e.g. p.399/4 either x or expN::x
If a namespace member and a global identifier or a block identifier have the same name
namespace_name :: must precede the namespace member
e.g. p.398/2 expN::x
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

35. The string Type p.1475
To use the data type string, the program must include the header file <string> p.1475
The statement:
string name = "William Jacob";
declares name to be a string variable and also initializes name to "William Jacob"
The first character, 'W', in name is in position 0,
the second character, 'i', is in position 1, and so on
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

36. The string Type (continued)
The variable name is capable of storing any size string
Binary operator + (to allow the string concatenation operation), and the array subscript operator [ ], have been defined for the data type string
If str1 = "Sunny", the statement stores the string "Sunny Day" into str2:
str2 = str1 + " Day";
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

37. length Function
Length returns the number of characters currently in the string
The syntax to call the length function is:
strVar.length()
where strVar is variable of the type string
no arguments
length returns an unsigned integer
The value returned can be stored in an integer variable
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

38. size Function The function size is same as the function length
Both functions return the same value
The syntax to call the function size is:
strVar.size()
where strVar is variable of the type string
has no arguments
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

39. find Function
find searches a string for the first occurrence of a particular substring
Returns an unsigned integer value of type string::size_type (an unsigned integral (data) type)
giving the result of the search
The syntax to call the function find is:
strVar.find(strExp)
where strVar is a string variable and strExp is a string expression evaluating to a string
The string expression, strExp, can also be a character
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

40. find Function (continued)
If successful, find returns the position in strVar where the match begins
For the search to be successful the match must be exact
If unsuccessful, find returns the special value string::npos (“not a position within the string”) – max value of data type string
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

41. substr Function substr returns a particular substring of a string
The syntax to call the function substr is:
strVar.substr(expr1,expr2)
where expr1 and expr2 are expressions evaluating to unsigned integers
The expression expr1 specifies a position within the string (starting position of the substring)
The expression expr2 specifies the length of the substring to be returned
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

42. swap Function swap interchanges the contents of two string variables
The syntax to use the function swap is
strVar1.swap(strVar2);
where strVar1 and strVar2 are string variables
Suppose you have the following statements:
string str1 = "Warm";
string str2 = "Cold";
After str1.swap(str2); executes, the value of str1 is "Cold" and the value of str2 is "Warm"
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

43. Programming Example: Pig Latin Strings p.410
Program prompts user to input a string
Then outputs the string in the pig Latin form
The rules for converting a string into pig Latin form are as follows:
If the string begins with a vowel, add the string "-way" at the end of the string
For example, the pig Latin form of the string "eye" is "eye-way“
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

44. Pig Latin Strings (continued)
If the string does not begin with a vowel, first add "-" at the end of the string
Then move the 1st of the string to the end of the string until the first character of the string becomes a vowel
Next, add the string "ay" at the end
For example, the pig Latin form of the string "There" is "ere-Thay“
For this program the vowels are a, e, i, o, u, y, A, E, I, O, U, and Y the pig Latin form of "by" is "y-bay“
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

45. Pig Latin Strings (continued)
Strings such as "1234" contain no vowels
The pig Latin form of a string that has no vowels in it is the string followed by the string "-way“
For example, the pig Latin form of the string "1234" is "1234-way“
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

46. Problem Analysis If str denotes a string
Check the first character, str[0], of str
If str[0] is a vowel, add "-way" at the end of str
If the first character of str, str[0], is not a vowel
First add "-" at the end of the string
Remove the first character of str from str and put it at end of str
Now the second character of str becomes the first character of str
This process is repeated until either
The first character of str is a vowel
All characters of str are processed, in which case str does not contain any vowels
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

47. Algorithm Design The program contains the following functions:
isVowel - to determine whether a character is a vowel
rotate - to move first character of str to the end of str
pigLatinString - to find the pig Latin form of str
Main Algorithm:
Get str
Use the function pigLatinString to find the pig Latin form of str
Output the pig Latin form of str
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

48. Function isVowel bool isVowel(char ch) { switch(ch)
case 'A': case 'E':
case 'I': case 'O':
case 'U': case 'Y':
case 'a': case 'e':
case 'i': case 'o':
case 'u': case 'y': return true;
default: return false; }
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

49. Function rotate (continued)
string rotate(string pStr) // Takes a string as a parameter {
int len = pStr.length();
string rStr;
rStr = pStr.substr(1,len - 1) + pStr[0]; // Removes 1st
// chr and places it at end
return rStr; }
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

50. // Pig Latin Strings p.410 string rotate(string pStr) {
#include <iostream>
#include <string>
using namespace std;
bool isVowel(char ch);
string rotate(string pStr);
string pigLatinString(string pStr);
int main() {
string str;
cout << "Enter a string: ";
cin >> str;
cout << endl;
cout << "The pig Latin form of " << str << " is: "
<< pigLatinString(str) << endl;
return 0; }
bool isVowel(char ch)
switch (ch)
case 'A': case 'E':
case 'I': case 'O':
case 'U': case 'Y':
case 'a': case 'e':
case 'i': case 'o':
case 'u': case 'y': return true;
default: return false;
string rotate(string pStr) {
string::size_type len = pStr.length();
string rStr;
rStr = pStr.substr(1, len - 1) + pStr[0];
return rStr; }
string pigLatinString(string pStr) // see next slide
string::size_type len;
bool foundVowel;
string::size_type counter;
if (isVowel(pStr[0])) //Step 1
pStr = pStr + "-way";
else //Step 2
pStr = pStr + '-';
pStr = rotate(pStr); //Step 3
len = pStr.length(); //Step 3.a
foundVowel = false; //Step 3.b
for (counter = 1; counter < len - 1; counter++)//Step 3.d
if (isVowel(pStr[0]))
foundVowel = true; break;
else //Step 3.c
pStr = rotate(pStr);
if (!foundVowel) //Step 4
pStr = pStr.substr(1, len) + "-way";
else
pStr = pStr + "ay";
return pStr; //Step 5
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

51. string pigLatinString(string pStr) { string::size_type len;
bool foundVowel;
string::size_type counter;
if (isVowel(pStr[0])) //Step 1
pStr = pStr + "-way";
else //Step 2
pStr = pStr + '-';
pStr = rotate(pStr); //Step 3
len = pStr.length(); //Step 3.a
foundVowel = false; //Step 3.b
for (counter = 1; counter < len - 1; counter++)
if (isVowel(pStr[0]))
foundVowel = true; break; }
else //Step 3.c
pStr = rotate(pStr);
if (!foundVowel) //Step 4
pStr = pStr.substr(1, len) + "-way";
else
pStr = pStr + "ay";
return pStr; //Step 5
1. If pStr[0] is a vowel, add "-way" at end of pStr
2. If pStr[0] is not a vowel
3a. Move the first character of pStr to the end of pStr
The second character of pStr becomes the first character of pStr
Now pStr may or may not contain a vowel
3b. Use a Boolean variable, foundVowel, which is set to true if pStr contains a vowel and false otherwise
initialize foundVowel to false
3c. if pStr[0] is not a vowel, move str[0] to the end of pStr by calling the function rotate
repeat above step until either the first character of pStr becomes a vowel or all characters of pStr have been checked
4. Convert pStr into the pig Latin form
5. Return pStr
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

52. Summary An enumeration type is a set of ordered values
Reserved word enum creates an enumeration type
No arithmetic operations are allowed on the enumeration type
Relational operators can be used with enum values
Enumeration type values cannot be input or output directly
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

53. Summary
An anonymous type is one where a variable’s values are specified without any type name
C++’s reserved word typedef creates synonyms or aliases to previously defined data types
The namespace mechanism is a feature of ANSI/ISO Standard C++
A namespace member is usually a
named constant,
variable,
function, or
another namespace
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

54. Summary The keyword namespace must appear in the using statement
A string is a sequence of zero or more characters
Strings in C++ are enclosed in double quotation marks
In C++, [] is called the array subscript operator
The function length returns the number of characters currently in the string
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

55. Summary
The function size returns the number of characters currently in the string
The function find searches a string to locate the first occurrence of a particular substring
The function substr returns a particular substring of a string
The function swap is used to swap the contents of two string variables
C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004