C++ Plus Data Structures

expanded by J. Goetz

1

C++ Plus Data Structures

Nell Dale

David Teague

Chapter 2

Data Design and ImplementationSlides by Sylvia Sorkin, Community College of Baltimore County - Essex Campus


2

Data

• The representation of information in a manner suitable for communication or analysis by humans or machines

• Data are the nouns of the programming world: – The objects that are manipulated– The information that is processed


3

Data Abstraction

• Separation of a data type’s logical properties (domain and operations) from its implementation.– e.g. declare an int type variable and operations are

allowed: =, +, -, *,/, %

LOGICAL PROPERTIES IMPLEMENTATION

What are the possible values? How can this be done in C++?

What operations will be needed? How can data types be used?


4

Data Abstraction

Whether we use

• functional decomposition producing a hierarchy of tasks or

• object-oriented design producing a hierarchy of cooperating objects,

data abstraction is essential.


5

APPLICATION

0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 1

REPRESENTATION

Data Encapsulation

• is the separation of the representation of data from the applications that use the data at a logical level; a programming language feature that enforces information hiding.

• The user of the data doesn’t see the implementation, but deals with its abstraction.

int y;

y = 25;


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Encapsulated C++ Data Type int

Value range: INT_MIN . . INT_MAX

Operations: + prefix - prefix + infix - infix * infix / infix % infixRelational Operators Equality Operators

TYPE int

inside

Representation ofint

as 16 bits two’s complement

+Implementation of Operations


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Abstract Data Type (ADT)

• A data type whose logical properties (domain and operations) are specified independently of any particular implementation (so you don’t worry about implementation, the lower level is hidden).

– Domain: int y;– Operations:

• create variables by declarations,

• assign values by using “=“,• reading by using arithmetic

operators• etc.

• The goal of design is to reduce complexity through abstraction and protect our data abstraction through encapsulation.


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ADT vs Data StructureADT

The logical picture of the data and the operations that manipulate them

Data Structure • 1. The concrete implementation of the data.• 2. A collection of data elements whose

organization (arrangement ) is characterized by accessing operations that are used to store and retrieve the individual data elements;

• 3. The implementation of the composite data members in an abstract date type


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Data Structure

1. The logical arrangement of data elements, combined with

2. The set of operations we need to access the elements


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Data Structures

• Data Structures can be – Decomposed into their components– Arrange that affects how each element is

accessed– The arrangement can be encapsulated

• An abstract data type (ADT) is implementation independent and a data structure is implementation dependent.


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• Application (or user) level: modeling real-life data in a specific context.

• Logical (or ADT) level: abstract view of the domain (the data values) and operations. WHAT question

• ADT Implementation level: specific representation of the structure to hold the data items, and the algorithm for operations.

• HOW question

Data from 3 different levels in modeling data in a program


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Viewing a library from 3 different levels

• Application (or user) level: Library of Congress, or Baltimore County Public Library.

• Logical (or ADT) level: What is a library?; domain is a collection of books; (What are) operations include: check book out, check book in, pay fine, reserve a book.

• Implementation level: representation of the structure to hold the “books”, and the coding for operations. – How are the books cataloged? A decimal system. How are they

organized on the shelf? 4 leves with 20 shelvs on each level. How does the librarian process a book when it is checked in? p.58 etc.


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Modeling Data Goal in Program

•1. Determine the logical picture of the data (ADT)

•2. Choose the representation and arrangement of the data

•3. Develop the operations that encapsulate this arrangement.


4 Basic Kinds of ADT Operations• Constructor -- creates a new instance (object) of an

ADT. • Transformer -- changes the state of one or more of the

data values of an instance.– e.g. insert/delete an item, making an object empty , a[1] = 5

• Observer -- allows us to observe the state of one or more of the data values without changing them. – e.g. accessor/selector functions that return a copy of an item, val = a[1];

summary functions about the object as a whole - # of items in the object; Boolean functions that returns true if an object empty

• Iterator -- allows us to process all the components in a data structure sequentially.– e.g. return successive list items

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Composite Data Type

A composite data type is a type which

• stores a collection of individual data components under one variable name,

• and allows the individual data components to be accessed.


Two Forms of Composite Data Types

Components are not organized with respect to one another.

The organization determines method used to access individual data components.

UNSTRUCTURED STRUCTURED

EXAMPLES: EXAMPLES: arraysclasses and structs, unions

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17

C++ Built-In Data Types

Composite

array struct union class

Address

pointer reference

Simple

Integral Floating

char short int long enum

float double long double


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Records

A record is a composite data type made up of a finite collection of not necessarily homogeneous elements called members or fields. For example . . .

.year 1999

.maker ‘h’ ‘o’ ‘n’ ‘d’ ‘a’ ‘\0’ . . .

.price 18678.92

thisCar at Base Address 6000


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struct CarTypestruct CarType{

int year ; char maker[10];

float price ;

} ;

CarType thisCar; //CarType variables

CarType myCar;


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Accessing struct members

The member selection operator (period . ) is used between the record variable name and the member identifier (selector) to access individual members of a record (struct or class) type variable.

EXAMPLESmyCar.yearthisCar.maker[4]


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Valid struct operations

• Operations valid on an entire struct type variable:

1. assignment to another struct variable of same type,

2. pass as a parameter to a function

(either by value or by reference),

3. return as the value of a function.


Pass-by-value

CALLINGBLOCK

FUNCTION CALLED

sends a copy of the contents of the actual parameter

SO, the actual parameter cannot be changed by the function. 22


Pass-by-reference

sends the location (memory address)of the actual parameter

can change value ofactual parameter

CALLINGBLOCK FUNCTION

CALLED

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Implementation level using struct type Reference Parameter to change a member

void AdjustForInflation(CarType& car, float perCent)

// Increases price by the amount specified in perCent{

car.price = car.price * perCent + car.price; } ;

SAMPLE CALL

AdjustForInflation(myCar, 0.03);


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Using struct type Value Parameter to examine a member

bool LateModel(CarType car, int date)

// Returns true if the car’s model year is later than or// equal to date; returns false otherwise.{

return ( car.year >= date ) ;

} ;

SAMPLE CALL

if ( LateModel(myCar, 1995) )std::cout << myCar.price << std::endl ;


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One-Dimensional Array at the Logical Level

A one-dimensional array is a structured composite data type made up of a finite, fixed size (known at compile time) collection of ordered homogeneous (all of the same data type) elements having relative positions and to which there is direct access (any element can be accessed immediately without accessing preceding elements).

Syntax of the declaration:

DataType arrayName [ConstIntExpression];

ConstIntExpression is an integer expression composed only literal or named constants e.g. MAX).


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One-Dimensional Array

Syntax of the component selector:

array-Name[IndexExpression]Whatever the form of the expression, it must result in an integer value.

• Array operations (creation) are performed using a declaration and (storing a value, retrieving a value) using indexes.


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Implementation Level

float values[5]; //it serves as a primitive constructor operation // assume element size is 4 bytes

This ACCESSING FUNCTION gives position of values[Index]

Address(Index) = BaseAddress + Index * SizeOfElement

Base Address

values[0] values[1] values[2] values[3] values[4]

7000 7004 7008 7012 7016

Indexes


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One-Dimensional Arrays in C++

• The index must be of an integral type (char, short, int, long, or enum).

• The index range is always 0 through the array size minus 1.

Valid struct operations1. Arrays cannot be assigned,

2. and cannot be the return type of a function.


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Another Example

char name[10]; // assume element size is 1 byte

The arrangment of this array in memory

name[0] name[1] name[2] name[3] name[4] . . . . . name[9]

Offset = Index * SizeOfElement

6000 6001 6002 6003 6004 6005 6006 6007 6008 6009

Base Address

This ACCESSING FUNCTION gives position of name[Index]

Address(Index) = BaseAddress + Index * SizeOfElement


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Passing Arrays as Parameters

• In C++, arrays are always passed by reference, and & is not used (omitted) ! with the formal parameter type.

• Whenever an array is passed as a parameter, its base address is sent to the called function.


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const array parameter

Because arrays are always passed as reference parameters, you can protect the actual parameter from unintentional changes by using const in formal parameter list and function prototype.

FOR EXAMPLE . . . // prototype

float SumValues( const float values[ ],

int numOfValues );

float SumValues (const float values[ ], /* the compiler needs to know that is an array; separate parameter is passed for the # of elements */ int numOfValues )

// Pre: values[ 0] through values[numOfValues-1] // have been assigned// Post: Returns the sum of values[0] through values[numOfValues-1]{ float sum = 0;

for ( int index = 0; index < numOfValues; index++ ) {

sum += values [ index ] ; }

return sum;}

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Two-Dimensional Array at the Logical Level

A two-dimensional array is a structured composite data type made up of a finite, fixed size collection of homogeneous elements having relative positions and to which there is direct access.

Array operations (creation) are performed using a declaration and (storing a value, retrieving a value) using a pair of indexes (called row and column) representing the component’s position in each dimension.


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EXAMPLE -- To keep monthly high temperatures for 50 states in a two-dimensional array. const int NUM_STATES = 50 ;const int NUM_MONTHS = 12 ;int stateHighs [ NUM_STATES ] [ NUM_MONTHS ] ;

[ 0 ]

[ 1 ] [ 2 ] . . stateHighs [2] [7] . [ 48 ] [ 49 ]

[0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

66 64 72 78 85 90 99 115 98 90 88 80row 2,col 7might beArizona’shigh forAugust


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Finding the average high temperature for Arizona

int total = 0 ;

int month ;

int average ;

for ( month = 0 ; month < NUM_MONTHS ; month ++ )

total = total + stateHighs [ 2 ] [ month ] ;

average = int ( total / 12.0 + 0.5 ) ;


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const int NUM_STATES = 50 ;const int NUM_MONTHS = 12 ;int stateHighs [ NUM_STATES ] [ NUM_MONTHS ] ;

• In memory, C++ stores arrays in row order. The first row is followed by the second row, etc.

12 highs for state 0 12 highs for state 1 etc. Alabama Alaska first row second row

8000 8024 8048

Base Address

Implementation level - STORAGE

. . .

rows columns


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Implementation Level ViewstateHighs[ 0 ] [ 0 ]stateHighs[ 0 ] [ 1 ]stateHighs[ 0 ] [ 2 ]stateHighs[ 0 ] [ 3 ]stateHighs[ 0 ] [ 4 ]stateHighs[ 0 ] [ 5 ]stateHighs[ 0 ] [ 6 ]stateHighs[ 0 ] [ 7 ]stateHighs[ 0 ] [ 8 ]stateHighs[ 0 ] [ 9 ]stateHighs[ 0 ] [10 ]stateHighs[ 0 ] [11 ]stateHighs[ 1 ] [ 0 ]stateHighs[ 1 ] [ 1 ]stateHighs[ 1 ] [ 2 ]stateHighs[ 1 ] [ 3 ] . . .

To locate an element such asstateHighs [ 2 ] [ 7] the compiler needs to know that there are 12 columnsin this two-dimensional array.

At what address will stateHighs [ 2 ] [ 7 ] be found?

Assume 2 bytes for type int.

Base Address 8000


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Two-Dimensional Array Parameters

• Just as with a one-dimensional array, when a two- (or higher) dimensional array is passed as a parameter, the base address of the actual array is sent to the function.

• The size of all dimensions except the first must be included in the function heading and prototype.

• The sizes of those dimensions for the formal parameter must be exactly the same as in the actual array.


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const int NUM_STATES = 50 ;const int NUM_MONTHS = 12 ;int stateHighs [ NUM_STATES ] [ NUM_MONTHS ] ;int stateAverages [ NUM_STATES ] ;

[ 0 ] ? [ 1 ] ? [ 2 ] . . . [ 48 ] [ 49 ]

[0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

43 42 50 55 60 78 79 80 77 72 63 4066 64 72 78 85 90 99 115 98 90 88 80

Use the two-dimensional stateHighs array to fill a

one-dimensional stateAverages array

Alaska

Arizona

void FindAverages( /* in */ const int stateHighs [ ] [ NUM_MONTHS] , /* in/out */ int stateAverages [ ] )

// Pre: stateHighs[ 0..NUM_STATES-1] [ 0..NUM_MONTHS-1] assigned// Post: stateAverages[ 0..NUM_STATES-1 ] contains rounded average// high temperature for each state{

int state; int month; int total; for ( state = 0 ; state < NUM_STATES; state++ ) {

total = 0 ; for ( month = 0 ; month < NUM_MONTHS ; month++ )

total += stateHighs [ state ] [ month ] ;stateAverages [ state ] = int ( total / 12.0 + 0.5 ) ;

}} 41


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Finding the Average High Temperature for Arizonaenum StateType { AL, AK, AZ, AR, CA, CO, CT, DE, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME,

MD, MA, MI, MN, MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VT, VA, WA, WV, WI, WY };

enum MonthType { JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC } ;

const int NUM_MONTHS = 12 ;const int NUM_STATES = 50 ;int stateHighs [ NUM_STATES ] [ NUM_MONTHS ] ;

int total = 0 ;MonthType month ; // WITH ENUM TYPES DEFINEDint average ;

for ( month = JAN ; month <= DEC ; month = MonthType( month + 1) ) total = total + stateHighs [ AZ] [ month ] ;average = int ( total / 12.0 + 0.5 ) ;


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Using typedef with arrayshelps eliminate the chances of size mismatches between

formal and actual parameters. FOR EXAMPLE,

typedef int StateHighsType [ NUM_STATES ] [ NUM_MONTHS ] ;

typedef int StateAveragesType [ NUM_STATES ] ;

void FindAverages( /* in */ const StateHighsType stateHighs , /* out */ StateAveragesType stateAverages )

{ . . .

}43


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Declaring Multidimensional Arrays

EXAMPLE USING TYPEDEF

const int NUM_DEPTS = 5 ; // mens, womens, childrens, electronics, linens

const int NUM_MONTHS = 12 ;

const int NUM_STORES = 3 ; // White Marsh, Owings Mills, Towson

typedef long MonthlySalesType [NUM_DEPTS] [NUM_MONTHS] [NUM_STORES];

MonthlySalesType monthlySales;

const int NUM_DEPTS = 5 ; // mens, womens, childrens, electronics, linensconst int NUM_MONTHS = 12 ; const int NUM_STORES = 3 ; // White Marsh, Owings Mills, Towson

typedef long MonthlySalesType [NUM_DEPTS] [NUM_MONTHS] [NUM_STORES] ;

MonthlySalesType monthlySales; monthlySales[3][7][0]sales for electronics in August at White Marsh

12 MONTHS columns

5 D

EP

TS

ro

ws

3 STORES

sheets

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C++ class data type

1. A class is an unstructured type that encapsulates a fixed number of data components (data members) with the functions (called member functions) that manipulate them.

2. The predefined operations on an instance of a class are whole assignment and component access.


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Use of C++ data type class

• Variables of a class type are called objects (or instances) of that particular class.

• Software that declares and uses objects of the class is called a client.

• Client code uses public member functions (called methods in OOP) to handle its class objects.

• Sending a message means calling a public member function.


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class DateType Specification// SPECIFICATION FILE ( datetype.h )

class DateType // declares a class data type{

public : // 4 public member functions - accessed by the client code

void Initialize ( int newMonth , int newDay , int newYear ) ; // a transformer operation

int YearIs( ) const ; // returns year – an accessor functionint MonthIs( ) const ; // returns month – an accessor int DayIs( ) const ; // returns day – an accessor

private :// 3 private data members – cannot be accessed by the client code, accessed by the class member functions

int year ; int month ; int day ;

} ; 48


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2 separate files generally used for class type

// SPECIFICATION FILE ( datetype .h ) // Specifies the data and function members. class DateType { public: . . .

private: . . . } ;

// IMPLEMENTATION FILE ( datetype.cpp ) // Implements the DateType member functions. . . .


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Implementation of DateType member functions

// IMPLEMENTATION FILE (datetype.cpp)#include “datetype.h” // also must appear in client code

void DateType :: Initialize ( int newMonth, int newDay, int newYear )// Post: year is set to newYear.// month is set to newMonth.// day is set to newDay.{

year = newYear ; month = newMonth ; day = newDay ;}

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int DateType :: MonthIs ( ) const// Accessor function for data member month{ return month ;}

int DateType :: YearIs ( ) const// Accessor function for data member year{ return year ;}

int DateType :: DayIs ( ) const// Accessor function for data member day{ return day ;}

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Client Code Using DateType#include “DateType.h” // includes specification of the class#include “Bool.h”using namespace std;int main ( void ){

DateType startDate ; // declares 2 objects of DateType DateType endDate ; bool retired = false ; startDate.Initialize ( 6, 30, 1998 ) ; endDate.Initialize ( 10, 31, 2002 ) ;

cout << startDate.MonthIs( ) << “/” << startDate.DayIs( ) << “/” << startDate.YearIs( ) << endl;

while ( ! retired ) { finishSomeTask( ) ; . . . } }

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DateType Class Instance Diagrams

Initialize

YearIs

MonthIs

DayIs

startDate endDate

Private data:

year

month

day

2002

10

31

Initialize

YearIs

MonthIs

DayIs

1998

6

30

Private data:

year

month

day


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Familiar Class Instances and Member Functions

• The member selection operator ( . ) selects either data members or member functions.

• Header files iostream and fstream declare – the istream, ostream,and ifstream, ofstream I/O classes.

• Both cin and cout are class objects and get and ignore are member functions.

cin.get (someChar) ;cin.ignore (100, ‘\n’) ;

• These statements declare myInfile as an instance of class ifstream and invoke member function open.

ifstream myInfile ;myInfile.open ( “A:\\mydata.dat” ) ;


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Scope Resolution Operator ( :: ) • C++ programs typically use several class types.

• Different classes can have member functions with the same identifier, like Write( ).

• Member selection operator is used to determine the class whose member function Write( ) is invoked. currentDate .Write( ) ; // class DateTypenumberZ .Write( ) ; // class ComplexNumberType

• In the implementation file, the scope resolution operator is used in the heading before the member function’s name to specify its class. void DateType :: Write ( ) const{ . . .

}


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Object-Oriented Programming• Three inter-related constructs: classes,

objects, and inheritance• Objects are the basic run-time entities in an

object-oriented system.• An object is a class object or class instance

(an instance of a class type)• A class defines the structure of its objects.• Classes are organized in an “is-a” hierarchy

defined by inheritance (every object of a derived class is also an object of the base class)


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Inheritance

1. Allows programmers to create a new class that is a specialization of an existing class.

2. The new class is called a derived class of the existing class; the existing class is the base class of the new class.

3. Each descendant (child) class inherits the properties (data and operations) of its ancestors (parents) class

4. The child doesn’t have access to parents’ private variables, only via parents’ public functions


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Inheritance

• Inheritance and polymorphism combined allow the programmer to build useful hierarchies of classes that can be reused in different applications

• Mapping of problem into solution


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# include <string>class MoneyType{public: void Initialize(long, long); long DollarsAre( ) const; long CentsAre( ) const;private: long dollars; long cents;};

class ExtMoneyType:public MoneyType

{public: string CurrencyIs( ); void Initialize(long, long, const string);private: string currency;};

ExtMoneyType extMoney;

void ExtMoneyType::Initialize

(long newDollars, long newCents, string newCurrency)

{

currency = newCurrency;

MoneyType::Initialize(

newDollars, newCents);

}

String ExtMoneyType::CurrencyIs()

const

{

return currency;

}


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Exceptions• An exception is an unusual situation that occurs

when the program is running.

• Exception Management – Define the error condition

– Enclose code containing possible error (try clause).

– Alert the system if error occurs (throw statement).

– Handle error if it is thrown (catch clause).


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try, catch, and throw// Reading and summing positive values from a filetry // code that contains a possible error{infile >> value;if (value < o) throw string(“An error has occurred in function …”); // a string is thrown; // catch has a string as a parametersum = sum + value;}

// error handler :catch (string message) //syntax: catch( exceptionType variable) –

//catch (type of the exception and the catch parameter) {

std::cout << message << std::endl;return 1;

}std::cout << “Sum of value on the file: “ << sum;


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Namespace = named scope

C++ language technique for grouping together a collection of names that logically belong together.

// in header file

namespace mySpace{

// All variables and functions prototypes within this// block must be accessed using scope// resolution operator (::).

}Purpose: Avoid namespace pollution when the same

name is used many times. Names can be grouped in the different namespace definition.


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Three Ways to Access Members within a Namespace

•Qualify each reference: mySpace::name with every reference.

•Using declaration: using mySpace::name;All future individual references to name refer to mySpace::name.

•Using directive:using namespace mySpace;All members of mySpace can be referenced without qualification.ex. using namespace std; // then you have access cout and cin


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Rules for Use of Namespace std(within text)

• Qualify names in prototypes and/or function definitions.

• If name used more than once in a function block, use a using declaration.

• If more than one name is used from a namespace, use a using directive.

• More about “Access to Identifiers in a Namespace” text p.98-99 or CS121 text 3 rd ed. ch.8 p.379-380


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Information Hiding

Class implementation details are hidden from the client’s view. This is called information hiding.

Public functions of a class provide the interface between the client code and the class objects.

clientcode

specification implementation

abstraction barrier

// SPECIFICATION FILE ( strtype.h )#include <fstream>#include <iostream>const int MAX_CHARS = 200 ;enum RelationType { LESS, EQUAL, GREATER } ;enum InType { ALPHA_NUM, ALPHA, NON_WHITE, NOT_NEW } ;class StrType // declares class data type{public : // 7 public member functions

void MakeEmpty ( ) ; void GetString ( bool skip, InType charsAllowed ) ;

void GetStringFile ( bool skip, InType charsAllowed, std::ifstream& inFile ) ;

void PrintToScreen ( bool newLine ) const ; void PrintToFile ( bool newLine, std::ofstream& outFile) const ;

int LengthIs( ) const ; void CopyString( StrType& newString ) const ;

private : // 1 private data memberchar letters [MAX_CHARS + 1 ] ;

} ;66


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StrType Class Interface Diagram

StrType class

Private data:

letters

GetString

GetStringFile

CopyString

LengthIs

PrintToFile

MakeEmpty

PrintToScreen‘c’ ’a’ ’t’ ’\0’ ...

// IMPLEMENTATION FILE (strtype.cpp)

#include “strtype.h” // also appears in client code #include “<cstring>”

void StrType :: MakeEmpty ( )// Post: letters is empty string.{

letters[0] = ‘\0’ ;}

. . .

int StrType :: LengthIs ( ) const// Returns length of letters string.{

return strlen ( letters ) ;} 68

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