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C++ Programming: Program Design Including Data Structures, Second Edition

C++ Programming: Program Design Including Data Structures, Second Edition. Chapter 8: User-Defined Simple Data Types, Namespaces, and the string Type. Objectives. In this chapter you will: Learn how to create and manipulate your own simple data type — called the enumeration type

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C++ Programming: Program Design Including Data Structures, Second Edition

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  1. 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 valuestogether 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 definedby 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. name of new type list of all possible values of this new type 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 } ; 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 enumsports{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 • The statement: 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 enumType 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 enumType Variables stored as 0 stored as 1 stored as 2 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 • The following statements are illegal; popularSport++; //illegal popularSport--; //illegal C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

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

  14. More aboutenum 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 inputnor 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. 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” ; break ; case JUL : case AUG : case SEP : cout << “Summer quarter” ; break ; 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 { SchoolTypeschoolLevel ; int age ; int lastGrade ; cout << “Enter age : “ ; // prompt for information cin >> age ; 20 expanded by J. Goetz, 2004

  21. 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 ; else 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#includepreprocessor 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; • typedefdoes not create any new data types • typedefcreates 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. typedefstatement • beforebool 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 becomeglobal identifiers in the program • If a global identifierin 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 sameproblem 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 vendorsbegin 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 accessedoutside the namespace • One way is to use the syntax: namespace_name::identifier • To access the member rate of the namespaceglobalType, 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 namespaceglobalType; using namespacestd; 3. To simplify the accessing of aspecific namespace member: using namespace_name::identifier; e.g.usingglobalType::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 samename • 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: stringname = "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 • findsearches 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 valuestring::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 expr1andexpr2 are expressions evaluating to unsigned integers • The expression expr1 specifies a position within the string (starting position of the substring) • The expression expr2 specifies thelength 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 beginswith avowel, 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 • Ifstr denotes a string • Check the first character, str[0], of str • Ifstr[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 repeateduntil 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. 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 } // Pig Latin Strings p.410 #include <iostream> #include <string> usingnamespace 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': returntrue; default: returnfalse; } } C++ Programming: Program Design Including Data Structures, Second Edition expanded by J. Goetz, 2004

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