C++ overview

DATA STRUCTURES & ALGORITHMS

C++ WARM-UP

- PREM RANJAN

OUTLINE

• History and overview

• Basic features

• Parameter passing

• Classes

• Inheritance and virtual

• Header file

• IO

• Memory Management

• Big three: destructor, copy constructor, and assignment operator

• Const

• Template

HISTORY OF C++

• 1972: C language developed at Bell Labs

• Dennis Ritchie wrote C for Unix OS

• Needed C for work with Unix

• late 70s: C becomes popular for OS development by many vendors

• Many variants of the language developed

• ANSI standard C in 1987-89

HISTORY OF C++ (CONTINUED)

• early 80s: Bjarne Stroustrup adds OO features to C creating C++

• 90s: continued evolution of the language and its applications

• preferred language for OS and low level programming

• popular language for application development

• low level control and high level power

CONCEPTUALLY WHAT IS C++

• Alternatives:

• is it C, with lots more options and features?

• is it an OO programming language with C as its core?

• is it a development environment?

• On most systems it is a development environment, language, and library, used for both procedural and object oriented programming, that can be customized and extended as desired

VERSIONS OF C++

• ANSI C++

• Microsoft C++ (MS Visual C++ 6.0)

• Other vendors: Borland, Symantec, Turbo, …

• Many older versions (almost annual) including different version of C too

• Many vendor specific versions

• Many platform specific versions

• For this class: Unix / Linux based versions

• g++

CHARACTERISTICS OF C++ AS A COMPUTER LANGUAGE

• Procedural

• Object Oriented

• Extensible

• ...

OTHER OO LANGUAGES

• Smalltalk

• pure OO language developed at PARC

• Java

• built on C/C++

• objects and data types

• Eifel and others

WHAT YOU CAN DO WITH C++

• Apps (standalone, Web apps, components)

• Active desktop (Dynamic HTML, incl Web)

• Create graphical apps

• Data access (e-mail, files, ODBC)

• Integrate components w/ other languages

DISADVANTAGES OF C++

• Tends to be one of the less portable languages

• Complicated?

• 40 operators, intricate precedence, pointers, etc.

• can control everything

• many exceptions and special cases

• tremendous libraries both standard, vendor specific, and available for purchase, but all are intricate

• Aspects above can result in high maintenance costs

ADVANTAGES OF C++

• Available on most machines

• Can get good performance

• Can get small size

• Can manage memory effectively

• Can control everything

• Good supply of programmers

• Suitable for almost any type of program (from systems programs to applications)

OUTLINE


• Basic features


• Classes


• Header file

• IO


• Big three: destructore, copy constructor, and assignment operator

• Const

• Template

PRIMITIVE TYPES

• bool true or false (only C++)

• char 8/16-bit

• short 16-bit signed integer

• int 32-bit signed integer

• unsigned 32-bit unsigned integer

• long 32 / 64-bit signed integer

• float 32-bit floating point

• double 64-bit floating point

OPERATORS AND PRECEDENCE

• [ ] . • to access arrays elements / to access object methods and fields

• expr++ expr-- ++expr --expr !

• new (type)expr

• * / %

• + -

• << >> (integers only)

• < > >= <=

• == !=

• &

OPERATORS AND PRECEDENCE

• ^

• |

• && (booleans only)

• || (booleans only)

• ?:

• = += -= *= ….

• C++ allows operator overloading

PRECEDENCE EXAMPLE

• What is: 5 + 21 / 4 % 3

• = 5 + (21 / 4) % 3

• = 5 + ( 5 % 3)

• = 5 + 2

• = 7

EXPLICIT CASTING

• (type) expression

• Possible among all integer and float types

• Possible among some class references

• E.g. int i = (int) ( (double)5 / (double)3 )

IMPLICIT CASTING

• Applied automatically provided there is no loss of precision

• float double

• int double

• Example

• int iresult, i=3;

• double dresult, d=3.2;

• dresult = i/d => implicit casting dresult=0.9375

• iresult = i/d => error! Why? Loss in precision, needs explicit casting

CONTROL FLOW

if (boolean)

statement;

else if(boolean)

statement2;

else

statement3;

Booleans only, not integers!• if (i > 0) correct

• if (i = 2) correct / incorrect ?

SWITCH / CASE

• switch (controlVar)

{

case 'a' :

statement-1

break;

case 'b' :

statement-2

break;

default :

statement-3

break;

}

• Do not forget the break command to avoid surprise result!

LOOPS

while(<boolean>)

statement;

do

statement;

while(<boolean>)

for(init-expr; <boolean>; incr-expr)

statement;

SOME CONVENTIONS FOR VARIABLE NAMES

• Use letters and numbers

• Do not use special characters including spaces, dots, underlines, pound signs, etc.

• The first letter will be lower case

• Use variable names that are meaningful (except for occasional counters that we might call i, j, x, etc.)

• You can concatenate words, and capitalize each after the first, e.g., bankBal, thisAcctNum, totAmt

• If you abbreviate, be consistent. For example do not use both bankBal and totalBalance as variable names.

SOME CONVENTIONS FOR STRUCT AND CLASS NAMES

• In creating names of structs and classes, apply the same rules as for variable names, except the first character will be upper case

• Example:

• an object's name: myCar

• the struct or class name: Car

• Another Example: aPerson and Person

OUTLINE


• Basic features


• Classes


• Header file

• IO



• Const

• Template

PASSING PARAMETERS

• C++ allows for three different ways of passing parameters:

• Pass “by value”

• E.g. foo (int n)

• Appropriate for small objects (usually primitive types) that should not be altered by the function call

• Pass “by constant reference”

• E.g. foo(const T& myT)

• Appropriate for large objects that should not be altered by the function call

• Pass “by reference”

• E.g. foo(bool & errFlag)

• Appropriate for small objects that can be altered by the function call

• Array types are always passed “by reference”

PASSING BY VALUE

void square(int i)

{

i = i*i;

}

int main()

{

int i = 5;

square(i);

cout << i << endl;

}

PASSING BY REFERENCE

void square(int& i)

{

i = i*i;

}

int main()

{

int i = 5;

square(i);

cout << i << endl;

}

PASSING BY CONSTANT REFERENCE

void square(const int& i)

{

i = i*i;

}

int main()

{

int i = 5;

square(i);

cout << i << endl;

}

Wont work, why?

PASSING BY CONSTANT REFERENCE

int square(const int& i)

{

return i*i;

}

int main()

{

int i = 5;

cout << square(i) << endl;

}

Will it his work?

WHAT IS A REFERENCE?

• An alias – another name for an object.

int x = 5;

int &y = x; // y is a reference to x

y = 10;

• What happened to x?

• What happened to y? – y is x.

WHY ARE THEY USEFUL?

• When passing argument of large size (class type), can save space

• Sometimes need to change a value of an argument

• Can be used to return more than one value (pass multiple parameters by reference)

HOW ARE REFERENCES DIFFERENT FROM POINTERS?

Reference Pointer

int a = 10;

int b = 20;

int &c = a;

c = b;

What is the value of a?

int a = 10;

int b = 20;

int *c = &a;

c = &b;

OUTLINE


• Basic features


• Classes


• Header file

• IO



• Const

• Template

CLASSES

• Provide a mechanism for defining classes of objects.

• We can define the class of all computers to have certain characteristics.

• An instance of a computer is your home PC.

• Classes contain member variables and member functions.

CLASSES IN C++:WHY CREATE CLASSES / OBJECTS?

• Keeps all related info (i.e., data) together

• Refer to all the related info by one name

• Protect the information

• Hide methods that use or change the info

• Keep methods together with their related info

EXAMPLE OF BENEFITS OF CREATING AN OBJECT

• Keeps all related info (i.e., data) together

Person thisPerson;

Person thisPerson = new Person ("Bill", "Clinton", 52);

• Refer to all the related info by one name

thisPerson

• Protect the information

lastName = "Dole"; //normally data members are private, and member functions are public

CLASSES AND OBJECTS

Mammals

Humans Tigers

Hank Peggy Tony

class

classclass

inherits inherits

instance-ofinstance-of

EXAMPLE OF A SIMPLE CLASS

class Change

{

private:

int quarters;

int dimes;

public:

int getQuarters() {return quarters;}

int getDimes() {return dimes;}

void setQuarters(int aQuarters) {quarters = aQuarters;}

…...

void printChange()

{cout << "\nQuarters: " << quarters

<< " Dimes: " << dimes << endl;

}

};

MORE CLASS EXAMPLE

class human

{

// this data is private to instances of the class

int height;

char name[];

int weight;

public:

void setHeight(int heightValue);

int getHeight();

};

FUNCTION DEFINITIONS

void human::setHeight(int heightValue)

{

if (heightValue > 0)

height = heightValue;

else

height = 0;

}

int human::getHeight()

{

return(height);

}

EXAMPLE

// first we define the variables.

int height = 72;

int result = 0;

human hank;

//set our human’s height

hank.setHeight(height);

//get his height

result = hank.getHeight();

cout << “Hank is = “ << result <<

“inches tall” << endl;

Hank is 72 inches tall

Output

INSTANTIATING AN OBJECT

• The class definition does not create any objects

• Instantiating and constructing are equivalent words for building a new object based on the model (i.e., template) of the class

• Instantiating is done just like declaring a variable of a built in data type

• Instantiating is done by a constructor (sometimes called a constructor method)

• If the "class provider" does not provide a constructor, then the C++ compiler provides a default one automatically

• The default constructor does not provide values to the data members (i.e. the instance variables)

INSTANTIATING AN OBJECT (MORE)

• When the object is instantiated, memory is allocated

• Example of instantiation (implicit call of constructor)

Car myCar;

Elephant oneElephant, twoElephant;

• No initialization takes place

• Each object has its own memory allocation

• oneElephant and twoElephant are separate objects in different locations in memory

• Each is addressed individually by name or location

• Each data member is addressed individually using the object name and the data member name, for example:

oneElephant.age

twoElephant.name

REFERENCING AN OBJECT

• Each object has a name (or a location) which is assigned when the object is instantiated

• private data members are accessible only within the class

• since most data members are private, that means that these data items are accessed generally by means of member functions

• myElephant.age = 72; //won't work, assuming is declared as private

• myElephant.setAge(72); // will work

OUTLINE


• Basic features


• Classes


• Header file

• IO



• Const

• Template

INHERITANCE

• The power of object-oriented languages

• Enables reuse of fields/methods

• All parent fields included in child instantiation

• Protected and public fields and methods directly accessible to child

• Parent methods may be overridden

• New fields and methods may be added to the child

• Multiple inheritance

INHERITANCE (CONT’D)

class classname: public parentname {

private:

….;

public:

….;

//access to parent methods through

// parentname::methodname …

}

OUTLINE


• Basic features


• Classes


• Header file

• IO



• Const

• Template

HEADER FILE

• For complex classes, the member functions are declared in a header file and the member functions are implemented in a separate file.

• This allows people to look at the class definitions, and their member functions separately

• The header file needs to be included in your program when you use the classes defined in the head file

#include “Segment.H”

#include <iostream>

# INCLUDE

Insert header file at this point.

Use library header.

HEADER GUARDS

#ifndef __SEGMENT_HEADER__

#define __SEGMENT_HEADER__

// contents of Segment.H

//...

#endif

• To ensure it is safe to include a file more than once.

HEADER GUARDS

#ifndef __SEGMENT_HEADER__

#define __SEGMENT_HEADER__

// contents of segment.H

//...

#endif

• To ensure it is safe to include a file more than once.

If this variable is

not defined…Define it.

End of guarded area.

OUTLINE


• Basic features


• Classes


• Header file

• IO



• Const

• Template

OUTPUT

#include<iostream>

Tell compiler that we are doing I/O

cout

Object to which we can send data.

<<

operator for sending data.

endl `\n’ `\t’

Special symbols that we can send.

FORMATTING OUTPUT

ios::left left justify the output

ios::right right justify the output

ios::scientific use scientific notation for numbers

ios::hex print numbers in hexadecimal base

ios::dec print numbers in decimal base

ios::uppercase print all characters in upper case

cout.setf(long flag) cout.unsetf(long flag)

Set different formatting

parameters for next output.

Disable these formatting

parameters.

EXAMPLE

#include<iostream.h>

main()

{

cout.width(10); //sets width to 10

cout << “hello” << endl;

cout.setf(ios::left);

cout << “hello” << endl;

cout << 16 << endl;

cout.setf(ios::hex, ios::basefield);

cout << 16 << endl;

}

hello

hello

16

10

Output

INPUT

#include <iostream.h>

Tell the linker we are doing basic I/O

cin

The input object. It retrieves input from the keyboard

>>

The extractor operator.

EXAMPLE


main ()

{

int userInput;

cout << “Enter number:”;

cin >> userInput;

cout << “You entered ” <<

userInput << endl;

}

Enter number:12345

You entered 12345

Output

I/O FROM A FILE

• I/O from a file is done in a similar way.


#include <fstream.h>

main()

{

int inputNumber;

ofstream myOutputFile(“outfile”);

ifstream myInputFile(“infile”);

myOutputFile << “text to file.” << endl;

myInputFile >> inputNumber;

myOutputFile.close();

myInputFile.close();

}

#include <string>

#include <fstream>

#include <iostream>

#include <iomanip>

using namespace std;

int main(int argc, char *argv[])

{

// Check input

if(argc<2)

{

cout<<"Usage: "<<argv[0]<<" <filename>"<<endl;

return 0;

}

// Try to read from file

cout<<"Reading tokens from file '"<<argv[1]<<"':"<<endl;

ifstream in(argv[1]);

if(!in)

cout<<" - Could not read from file '"<<argv[1]<<"'."<<endl;

else

{

string token;

cout.setf(ios::right);

for(unsigned i=1; in>>token; i++)

cout<<setw(4)<<i<<": "<<token<<endl;

}

in.close();

cout<<endl;

// Allow user to enter a token

string text;

cout<<"Enter some text: ";

getline(cin, text);

// Append new tokens to file

ofstream out(argv[1], ios::app);

if(out)

out<<endl<<text<<endl;

else

cout<<"- Could not write to file '"<<argv[1]<<"'"<<endl;

out.close();

return 0;

}

This program reads a file

name given by the user and

the read token by token from

the file. The tokens are

printed to the standard

output.

The second half of the

algorithm reads a token from

a standard input and appends

it to the file that was given.

OUTLINE


• Basic features


• Classes


• Header file

• IO



• Const

• Template

WHAT IS A POINTER?

int x = 10;

int *p;

p = &x;

p gets the address of x in memory.

p

x10

WHAT IS A POINTER?

int x = 10;

int *p;

p = &x;

*p = 20;

*p is the value at the address p.

p

x20

WHAT IS A POINTER?

int x = 10;

int *p;

p = &x;

*p = 20;

Declares a pointer

to an integer

& is address operator

gets address of x

* dereference operator

gets value at p

A POINTER EXAMPLE

int main(){

int i, j;

int *pi, *pj;

i = 5;

j = i;

pi = &i;

pj = pi;

*pj = 4;

cout << i << “ “;

cout << j << “ “;

cout << *pi << “ “;

cout << *pj << endl;

return 0;

}

> 4, 5, 4, 4

ALLOCATING MEMORY USING NEW

Point *p = new Point(5, 5);

• Point is a class already defined

• new can be thought of a function with slightly strange syntax

• new allocates space to hold the object.

• new calls the object’s constructor.

• new returns a pointer to that object.

MEMORY ALLOCATION EXAMPLES

• new returns a pointer to the dynamically created object.

#include “Cow.h”

#include <iostream>


int main(){

int *i = new int(12);

Cow *c = new Cow;

...

delete i;

delete c;

return 0;

}

PROBLEMS

• Dangling pointers

• Pointers to memory that has already been deallocated

• segmentation fault (core dump)... or worse....

• Memory leak

• Loosing pointers to dynamically allocated memory

• Substantial problem in many commercial products

• See Windows 98

• C++ HAS NO GARBAGE COLLECTION!

DANGLING POINTER EXAMPLES

int main(){

int *myNum = new int(12);

int *myOtherNum = myNum;

delete myNum;

cout << *myOtherNum << endl;

return 0;

}

int* badFunction(){

int num = 10;

return &num;

}

int* stillBad(int n){

n += 12;

return &n;

}

int main(){

int num = 12;

int *myNum = badFunction();

int *myOtherNum = stillBad(num);

cout << *myNum << “, “;

cout << *myOtherNum << endl;

return 0;

}

MEMORY LEAK EXAMPLES

int main(){

int *myNum = new int(12);

myNum = new int(10);

// Oops...

delete myNum;

return 0;

}

int evilFunction(){

int *i = new int(9);

return *i;

}

int main(){

int num = evilFunction();

// I’m loosing my memory!!

return 0;

}

DEALLOCATING MEMORY USING DELETE

// allocate memory

Point *p = new Point(5, 5);

...

// free the memory

delete p;

For every call to new, there must be

exactly one call to delete.

USING NEW WITH ARRAYS

int x = 10;

int* nums1 = new int[10]; // ok

int* nums2 = new int[x]; // ok

• Initializes an array of 10 integers on the heap.

• C++ equivalent of C

int* nums = (int*)malloc(x * sizeof(int));

USING NEW WITH MULTIDIMENSIONAL ARRAYS

int x = 3, y = 4;

int* nums3 = new int[x][4][5];// ok

int* nums4 = new int[x][y][5];// BAD!

• Initializes a multidimensional array

• Only the first dimension can be a variable. The rest must be constants.

• Use single dimension arrays to fake multidimensional ones

USING DELETE ON ARRAYS

// allocate memory

int* nums1 = new int[10];

int* nums3 = new int[x][4][5];

...

// free the memory

delete[] nums1;

delete[] nums3;

• Have to use delete[].

OUTLINE


• Basic features


• Classes


• Header file

• IO



• Const

• Template

CLASS DESTRUCTORS

• If a class dynamically allocates memory, we need a way to deallocate it when it’s destroyed.

• Distructors called upon distruction of an object

class MyClass{

public:

MyClass(){

// Constructor

}

~MyClass(){

// Destructor

}

...

};

DESTRUCTORS

• delete calls the object’s destructor.

• delete frees space occupied by the object.

• A destructor cleans up after the object.

• Releases resources such as memory.

DESTRUCTORS – AN EXAMPLE

class Segment

{

public:

Segment();

virtual ~Segment();

private:

Point *m_p0, *m_p1;

};

DESTRUCTORS – AN EXAMPLE

Segment::Segment()

{

m_p0 = new Point(0, 0);

m_p1 = new Point(1, 1);

}

Segment::~Segment()

{

delete m_p0;

delete m_p1;

}

COPY CONSTRUCTOR AND ASSIGNMENT OPERATOR

• Copy Constructor:

class Rooster{

public:

...

Rooster(const Rooster &rhs){

// Do your deep copy

}

...

};

...

// Usage

Rooster r(12);

Rooster s(r);

• Assignment Operator:

class Rooster{

public:

...

Rooster&

operator=(const Rooster &rhs){

// Copy stuff

}

...

};

...

// Usage

Rooster r(12), s(10);

r = s;

CANONICAL FORM

• All classes should have each of the following:

• Default constructor

• Copy constructor

• Assignment operator

• Destructor

// Canonical Cow

class Cow{

public:

Cow(){...}

Cow(const Cow &rhs){...}

Cow& operator=(const Cow &c)

{...}

~Cow(){...}

...

};

OUTLINE


• Basic features


• Classes


• Header file

• IO



• Const

• Template

INTRODUCING: CONST

void Math::printSquare(const int& i)

{

i = i*i;

cout << i << endl;

}

int main()

{

int i = 5;

Math::printSquare(i);

Math::printCube(i);

}

Won’t compile.

HOW DOES CONST WORK HERE?

void Math::printSquares(const int& j, int& k)

{

k = k*k; // Does this compile?

cout << j*j << “, “ << k << endl;

}

int main()

{

int i = 5;

Math::printSquares(i, i);

}

RETURNING CONST REFERENCES IS OK

class Point

{

point:

const double& getX() const;

const double& getY() const;

void move(double dx, double dy);

private:

double m_x, m_y;

}

const double& Point::getX()

const

{

return m_x;

}

Constant function, also called accessor

Return a reference to a

constant double

NAMESPACES

• Namespaces are kind of like packages in Java

• Reduces naming conflicts

• Most standards C++ routines and classes and under the stdnamespace

USING NAMESPACE

#include <iostream>

...

std::string question =

“How do I prevent RSI?”;

std::cout << question << std::endl;


string answer = “Type less.”;

cout << answer << endl;

But, not in header files!

OUTLINE


• Basic features


• Classes


• Header file

• IO


• Big three: destructor, copy constructor, and assignment operator

• Const

• Template

TEMPLATE

What exactly are templates for, and why learn them?

• Limited Generic Programming (polymorphism)Some functions have the same semantic meaning for some (if not all) data

types. For instance, a function print() should display a sensible

representation of anything passed in. Ideally, it shouldn’t need to be

rewritten for each possible type.

• Less repetitive codeCode that only differs in the data type it handles does not have to be

rewritten for each and every data type you want to handle. It’s easier to

read and maintain since one piece of code is used for everything

EXAMPLE: A SWAP FUNCTION

Naive method – write an overloaded function for each type

void swap(int &a, int &b) {

int c = a;

a = b;

b = c;

}

void swap(T &a, T &b) {

T c = a;

a = b;

b = c;

}

Swap for integers Swap for an arbitrary type T

template <typename T>


T c = a;

a = b;

b = c;

}

This function can be used with any

type that supports assignment and can

be passed in as a non-const reference.

Problem: Oftentimes, it is nice to be able to swap the values of two variables. This function’s behavior is similar for all data types. Templated functions let you do that – in most cases without any syntax changes.

Template method – write one templated function

TEMPLATE SYNTAX: SWAP DISSECTED



T c = a;

a = b;

b = c;

}

The template<…> line states that everything in the following declaration or definition is under the subject of the template. (In this case, the definition is the function swap)

In here goes a list of “placeholders variables.” In almost all cases, they will be specified with either the typename or class keywords. These two keywords are equivalent.

“Placeholder variables” have one value within each template declaration. Think of them as being replaced by whatever type you specify the template to be.

TEMPLATE SYNTAX: USING IT



T c = a;

a = b;

b = c;

}

Example:double d1 = 4.5, d2 = 6.7;

swap(d1, d2);

Syntax

CLASS TEMPLATES: EXAMPLE

Example: A templated, dynamic, 2 dimensional array (Matrix)*

#ifndef MATRIX_H

#define MATRIX_H


class Matrix {

public:

Matrix(int rows, int cols);

Matrix(const Matrix &other);

virtual ~Matrix();

Matrix& operator=(const Matrix &rhs);

T* operator[](int i);

int getRows() const;

int getCols() const;

protected:

void copy(const Matrix &other);

private:

Matrix();

int m_rows;

int m_cols;

T *m_linArray;

};

#endif /* MATRIX_H */File: Matrix.h

Notice the only addition to the class definition is the line:template <typename T>

Within the the definition block, the placeholder has can be used as a data type. When the template is specialized, it takes on the value of the specialization.


T* Matrix<T>::operator[](int i) {

return m_linArray + (i*m_cols);

}


void

Matrix<T>::copy(const Matrix &other) {

m_rows = other.m_rows;

m_cols = other.m_cols;

int size = m_rows * m_cols;

m_linArray = new T[size];

for( int i=0; i < size; i++ ) {

m_linArray[i] =

other.m_linArray[i];

}

}


int Matrix<T>::getRows() const {

return m_rows;

}


int Matrix<T>::getCols() const {

return m_cols;

}

CLASS TEMPLATES: EXAMPLE CONT’D

#include "Matrix.h"


Matrix<T>::Matrix()

{}


Matrix<T>::Matrix(int rows, int cols) {

m_rows = rows;

m_cols = cols;

m_linArray = new T[m_rows * m_cols];

}


Matrix<T>::Matrix(const Matrix &other) {

copy(other);

}


Matrix<T>::~Matrix() {

delete[] m_linArray;

}


Matrix<T>&

Matrix<T>::operator=(const Matrix &other) {

if( this != &other ) {

delete[] m_linArray;

copy(other);

}

return *this;

} File: Matrix.cc


Matrix<T>&

Matrix<T>::operator=(const Matrix &other) {

if( this != &other ) {

this->~Matrix();

copy(other);

}

return *this;

}

CLASS TEMPLATES: MEMBER FUNCTIONS DISSECTED

Again, a templated class name by itself has no meaning (eg. Matrix by itself means nothing). It only gets meaning through specialization, explicit or implicit. Thus, when referring to an instance of a templated class (a specific specialization), the class name must be explicitly specialized.

Here, the template has been implicitly specialized by its context. It is within the specialization regionof the class scope. Thus it does not need the template arguments. For a class definition, the specialization region is the class block.

specialization region of

Matrix<T>::Notice that the specialization region does not include the return type. Thus the return type needs explicit specialization

This may be obvious, but remember that though constructors and destructors have the same name as a the class template, they are functions and do not need to be specialized.

CLASS TEMPLATES: USAGE

• Templated classes must be explicitly specialized. Thus, to create a 2 dimensional Matrix of doubles using the last example, the syntax would be:

Matrix<double> m(3,3);

Syntax

STL

• Allows you to easily store anything without writing a container yourself

• Will give you the most hideous compile errors ever if you use them incorrectly.

STL EXAMPLE


typedef list<int> intlist;

typedef intlist::iterator intlistIter;

intlist v;

v.push_back(4);

intlistIter a;

for(a = v.begin(); a != v.end(); ++a)

{

int c = (*a);

}

• Now compile and run a simple c++ program

COMPILATION MODEL

• Preprocessor

• Resolves all preprocessor directives

• #include, #define macros, #ifdef, etc.

• Compiler

• Converts text into object files

• May have unresolved interobject references

• Linker

• Resolves all interobject references (or gives you a linker error)

• Creates the binary executable

• Loader

• Loads the program into RAM and runs the main() function

COMPILATION

PreprocessorInlines #includes etc.

CompilerTranslates to machine code

Associates calls with functions

LinkerAssociates functions with definitions

Object files

Executable

External Libraries, libc.so, libcs123.so

HELLOWORLD.CPP

#include <iostream> // For cout


int main(){

cout << "Hello World!" << endl;

return 0;

}

COMPILING WITH G++

ix$ ls

hello.cpp

ix$ ls

hello.cpp

ix$ g++ hello.cpp

ix$ ls

a.out* hello.cpp

ix$ g++ -c hello.cpp

ix$ ls

a.out* hello.cpp hello.o

ix$ g++ -o hello hello.cpp

ix$ ./hello

Hello World!

MAKEFILE

> make

SIMPLE MAKEFILE

All: hello

hello: hello.o

g++ -o hello hello.o

hello.o: hello.cpp

g++ -c hello.cpp

ix$ ls

hello.cpp makefile

ix$ make

g++ -c hello.cpp

g++ -o hello hello.o

ix$ ls

hello* hello.cpp hello.o makefile

ix$ ./hello

Hello World!

Education

C++ overview