C++ WorkshopC++ Workshop

Mark HennessyMark Hennessy

Dept. Computer ScienceDept. Computer Science

1818thth – 22 – 22ndnd September 2006 September 2006

Week OutlineWeek Outline

• Monday – Intro to C++ Basics

• Tuesday – Classes, Overloading, Exceptions

• Wednesday – Defining Data Structures

• Thursday – OO Development in C++

• Friday – An introduction to the STL and templates.

Day outlineDay outline

• Lectures : 930 – 1100

• Assignment

• 1500: 90 mins later on in the day.

WorkstationWorkstation

• We will use MS Windows but GNU/Linux has more support for C++ development.

• Compiler is g++ from the GNU Compiler Collection, gcc.

• This course is about development in ISO/ANSI standard C++

• -> We will not be using Microsoft Visual C++!

Practical InfoPractical Info

• Work on the C:\ disk can only be saved in the temp folder.

• WARNING!!! If you leave your work in the temp folder and then log out it will be lost!

• Therefore save all of your work to your personal X:\ disk or on some USB storage.

C++ ResourcesC++ Resources

• Textbooks here in the lab.

• Online resources:

1. http://en.wikipedia.org/wiki/C++_standard_library

2. http://www.cplusplus.com/

3. http://www.sgi.com/tech/stl/

5 Kinds of Programmers5 Kinds of Programmers

• Those who can’t

• those who can without pointers

• those who can with pointers

• those who know object technology: OO

• those who can use generics/templates

Motivation for OO with C++Motivation for OO with C++

• C++/Java most widely used languages,

• OO is the way of the present,• familiarity increases marketability,• viable for many years,• excellent expressivity, and• excellent speed.• Easy to learn another language

Lots of “stuff”Lots of “stuff”

• There is an intimidating amount of material in C++

• C++ was designed to be a powerful tool for professional programmers solving real problems in diverse domains

• C++ was NOT designed for academia!• C++ was NOT designed to be a nice, “pure”

language, good for teaching students how to program

C++ IntroC++ Intro

• We need to learn the language, start with the syntax!

• Any Java programmers will be fine, C programmers will survive too!

• Lets get started….

Hello WorldHello World

#include <iostream>

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

{

std::cout<<“Hello World”<<std::endl;

}

IdentifiersIdentifiers

• An identifier must start with a letter or underscore, and be followed by zero or more letters

• C++ is case sensitive

• VALID

age_of_dog TaxRate98

PrintHeading AgeOfHorse

• INVALID examples - try to find them yourselves using the compiler

C++ Data TypesC++ Data Types

Structured

array struct union class

Address

pointer reference

Simple

Integral Floating

char short int long enum

float double long double

Typical size of data typesTypical size of data types

Type Number of Bytes

char 1

short (short int) 2

int 4

unsigned int 4

enum 2

long (long int) 4

float 4

double 8

long double 12

Finding size of data type - system dependent resultsFinding size of data type - system dependent results

• Use sizeofsizeof to find the size of a typee.g.std::cout << sizeof(int)

Enumerated types: Enumerated types: enumenum

Used to define constant values

enum days{ Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday} yesterday, today;

days tomorrow;

QUESTION: what are the values of Tuesday, today, tomorrow, yesterday?

Default values may be overridden in the enum list.

Boolean typeBoolean type

C++ has a built-in logical or Boolean type

#include <iostream.h>

int main (){bool flag = true;std::cout << flag<< std::endl<<!flag}

This outputs:

1

0

Variation - booleans are really integers?

//

#include <iostream.h>

int main (){bool flag1 = 100, flag2 = false, flag3;std::cout << flag1<< std::endl<<flag2<<std::endl<<flag3;}

This outputs:

1

0

122

true is any non-zero int

false is zero

true is output as 1false is output as 0

This was not initialised

Giving a value to a variable

In your program you can assign (give) a value to the variable by using the assignment operator =

Age_Of_Dog = 12;

or by another standard method, such as

std::cout << “How old is your dog?”;std::cin >> Age_Of_Dog;

What is a Named Constant?What is a Named Constant?

• A named constant is a location in memory which we can refer to by an identifier, and in which a data value that cannot be changed is stored.

VALID CONSTANT DECLARATIONS• const char STAR = ‘*’ ;• const float PI = 3.14159 ;• const int MAX_SIZE = 50 ;

keywords: words reserved to C++keywords: words reserved to C++

• bool, true, false,• char, float, int, unsigned, double, long• if, else, for, while, switch, case, break,

• class, public, private, protected, new,

delete, template, this, virtual,

• try, catch, throw.

Note: there are many more … you may see them in the examples that follow

Example 6: prefix and postfix

//

#include <iostream.h>

int main (){int x =3, y=3;std::cout << ++x << std::endl;std::cout << y++ << std::endl;}

Output: 43

++ (prefix) is a unary operator

++ (postfix) is a unary operator

<< is a binary operator

Example 7: a C+ ternary operator

// Example 7

#include <iostream.h>

int main (){int x =3, y=4;std::cout <<"The max. of x and y is: " << (x>y?x:y);}

The max. of x and y is: 4

expression1?expression2:expression3

Output:

Means: if expression1 then expression2 else expression3

Program with Three Functions

// #include <iostream>// declares these 2 functionsint Square ( int );int Cube ( int ) ;

int main ( void ){ std::cout << "The square of 27 is "<< Square (27) << std::endl ;// function call

std::cout << "The cube of 27 is "<< Cube (27) << std::endl ;// function call

return 0 ;}int Square ( int n ){return n * n ;}int Cube ( int n ){return n * n * n ;}The square of 27 is 729

The cube of 27 is 19683Output:

Precedence of Some C++ OperatorsPrecedence of Some C++ Operators

Precedence Operator Description

Higher ( ) Function call

+ Positive

- Negative

* Multiplication

/ Division

% Modulus (remainder)

+ Addition

- Subtraction

Lower = Assignment

NOTE: Write some programs to test your understanding of precedence

Type Casting is Explicit Conversion of TypeType Casting is Explicit Conversion of Type

// Example #include <iostream>

int main ( void ){ std::cout << "int(4.8) ="<<int(4.8)<<std::endl;std::cout << "float(5) ="<<float(5)<<std::endl;std::cout <<”float(2/4)="<<float(2/4)<<std::endl;std::cout<<"float(2)/float(4)

="<<float(2)/float(4)<<std::endl;}

int(4.8) =4float(5) =5float(2/4)=0float(2)/float(4)=0.5

Output:Output of float may look like an int

Parts of a FunctionParts of a Function

Every function has 2 parts

int main (void)

{

return 0;

}

signature

body

HEADER FILE FUNCTION EXAMPLEHEADER FILE FUNCTION EXAMPLE VALUE OF CALL VALUE OF CALL

std::fabs(x) std::fabs(-6.4) 6.4

<math> std::pow(x,y) std::pow(2.0,3.0) 8.0

std::sqrt(x) std::sqrt(100.0) 10.0

<iomanip> std::setprecision(n) std::setprecision(3)

std::log(x) std::log(2.0) 0.693147

std::sqrt(2.0) 1.41421

<stdlib> std::abs(i) std::abs(-6) 6

C++ I/O BasicsC++ I/O Basics

29

I/O - Input/Output is one of the first aspects of programming that needs to be mastered:

•formatting

•whitespace

•structured inputs - getting data into the correct internal form

However, do not fall into the beginner’s traps:

•brilliant I/O with incorrect functionality

•thinking functionality is wrong because I/O is too complicated to get right

•forgetting that random tests are often better than user dependent I/O

Whitespace Characters Include . . .Whitespace Characters Include . . .

• blanks• tabs ‘\t’• end-of-line (newline) characters ‘\n’

The newline character is created by hitting Enter or Return at the keyboard, or by using the manipulator endl or “\n” in a program.

E.g

std::cout << std::endl;

std::cout << “\n”;