copyright 2008 oxford consulting, ltd 1 october 2008 - 1 - c to c++ c++ comments can use the symbol...

Copyright 2008 Oxford Consulting, Ltd 1 October 2008

- 1 -

C to C++C to C++

C++ Comments

Can use the symbol //

To identify single line comments


- 2 -

C to C++C to C++

const SpecifierUsed to declare or specify a constant

const int speed = 60;

Transforms

Symbolic Variable

…. speed ….

Symbolic constant

…. speed ….

Within the scope of speed

speed = 85; // Illegal


- 3 -

C to C++C to C++

Const and Pointers

Object Pointer

*

ptr = “Hello”;

const ptr = “Hello”;

ptr = “Hello”;

char

const ptr = “Hello”;

char

const char

const char

*

*

*


- 4 -

C to C++C to C++

Declarations within BlocksCan declare variables within block after code segment

void main ()

{

int a;

….

code

int b;

more code (using b)

char* c;

yet more code (using c)

}


- 5 -

C to C++C to C++

Declarations within a Loopfor (int i = 0; i < 10; i++) {

for (int i = 2; i < 15; i++) {

for (int i = 4; i < 25; i++){…}// i from inner loop

}}i from outer loop…for (int i = 0; i >20; i--){}


- 6 -

C to C++C to C++

Functionsprototypes

void myDataDisplay( int, char*, float)

Parameter names are not necessary

Good style suggests using names

void myDataDisplay( int range, char* label, float value)


- 7 -

C to C++C to C++

Default Parameters

Trailing set or args is Initialized to Default Values

The Default Values are Specified in Prototype…..

void myFunction (int earth, int moon = 10, int stars = 20);

Can call the function with fewer args than the declared….

printThings (10);

printThings(10,20);

printThings (10, 20, 30);


- 8 -

C to C++C to C++

Overloading Function Names - Simple Polymorphism

Functions can use the same names within the same scopeIf ……….

Each function declaration and use can be distinguished by

Name and Signature

Signature

Number and type of parameters

char *s = "This is a string";printThings (10); // Print an intprintThings('a'); // Print a charprintThings (s); // Print a string

char *s = "This is a string";printThings (10); // Print an intprintThings('a'); // Print a charprintThings (s); // Print a string


- 9 -

C to C++C to C++

Overloading Function Names - Simple PolymorphismRedeclaration

If return type and signatures match…the arg names are irrelevant

extern void print (int a, int b);

void print (int c, int d);

Erroneous Redeclaration

If signatures match and return types differ

char print (int a, int b);

void print (int c, int d);

Overloaded

If signatures differ in the

Number, Type, or Order of args


- 10 -

C to C++C to C++

Reference Types - Definition

Serve as alias for an object

Must be initialized like a const

syntax

& operator following the type specifier in the declaration

int aValue = 20; // declare and define a value

int &speed = aValue;// declare and initialize a reference

speed += 10; // adds 10 to aValue


- 11 -

C to C++C to C++

Reference Types - Initialization

A reference of type T

Must be initialized by

Object of type T

Object that can be converted to a type T

Cannot be changed to refer to another object after initialization


- 12 -

C to C++C to C++

Reference Types - Initializationnon const

Initialized only by an lvalue of the exact type

Reference refers to initializer

const

Initialized only by an

rvalue

lvalue

Does not need to be of the exact type

Temporary object of type T created

Initialized with the initializer

Reference refers to the temporary


- 13 -

C to C++C to C++


unsigned char mine;int d1, d2;

int &a = 1024; // illegal 1024 is not an lvaluechar &b = mine; // illegal not exact typeint &c = d1 + d2; // illegal not an l value

const int &a = 1024; // okconst char &b = mine; // okconst int &c = d1 + d2; // ok

unsigned char mine;int d1, d2;

int &a = 1024; // illegal 1024 is not an lvaluechar &b = mine; // illegal not exact typeint &c = d1 + d2; // illegal not an l value

const int &a = 1024; // okconst char &b = mine; // okconst int &c = d1 + d2; // ok


- 14 -

C to C++C to C++


Initialization can be eliminated only in

Argument declaration

Declaration of a function return type

Declaration of a class member

Extern specifier used


- 15 -

C to C++C to C++

References vs. Pointers

References do not support pointer like operations

Cannot have …….

Pointers to references

Arrays of references

Consequence of first

int & v[ ] v[1] *(v+1)

Reference to reference

Reference to bit fields


- 16 -

C to C++C to C++

void increment (int* &i) {i++;}

int main( ){

int* iPtr = 0;

cout << "iPtr = " << iPtr << endl; // Prints 0x00000000

increment (iPtr);


return 0;}

void increment (int* &i) {i++;}

int main( ){

int* iPtr = 0;


increment (iPtr);


return 0;}


- 17 -

C to C++C to C++

References as ParametersPass by Value

Function never accesses the actual args

Manipulates a local copy stored on the stack

Changes made to the local copies

Do not affect the actual args

Pass by Reference

Function accesses the actual args

Address of the arg is passed

If arg is not to be changed use const

myFunction (const int &x)


- 18 -

C to C++C to C++

new and delete operators

To manage allocation and deallocation of memory at runtime

C has the functions

malloc

free

C++ introduces the operators

new

delete


- 19 -

C to C++C to C++


new operator

Gives programmer control over storage allocation from heap

at runtime

Similar to malloc

delete operator

Gives programmer control over storage deallocation at runtime

Similar to free


- 20 -

C to C++C to C++

new and delete operatorsnew Operator

syntax

new (nothrow) type [amount]

returns

On success

pointer to newly allocated memory

On failure

Exception or NULL

new type ( value )

Initializes the variable to value


- 21 -

C to C++C to C++


int *myPtr = new int;Allocate sufficient storage to hold a single integerPointer to storage assigned to myPtr

int * myPtr = new char [ strlen (“Bon jour mes amis”) + strlen (“touts les jour”) ];Returns a pointer to an area of memory to hold 17 + 14 characters

new int(23);Returns a pointer to an int initialized to 23


- 22 -

C to C++C to C++

new and delete operatorsdelete operator

“Destroys” object created by new…returns the memory to heap

No arguments

Return type void

syntax

delete expression

delete [ ] expression

In both cases expression pointer to memory allocated by new

Do not use delete to free an array

This operation is undefined


- 23 -

C to C++C to C++

new and delete operatorsDont’s

• Do not use delete to free an array

• Delete a single object with delete [ ]

• Apply delete operator to object not created by new

• Try to access a deleted object

• Try to delete a pointer to a const - that’s changing it

Deuze

• Use delete [ ] to free any objects created with new [ ]

• Use delete to free any objects created with new or new ( )


- 24 -

C to C++C to C++

int main( ){

char *stuff[ ] = {" is ", "getting ", "longer "};char *s = new char [strlen ("My string") +1];strcpy (s, "My string");for (int i = 0; i< 3; i++){ s = growString(s, stuff[i]); cout << s << endl;}return 0;

}

char *growString(char *myString, char *aString){

char *tString = new char [strlen(myString) + strlen(aString) + 1];strcpy (tString, myString);strcat (tString, aString);delete[ ] myString;

return tString;}


- 25 -

C to C++C to C++

Enumeration Types

The name of an enumeration is a type name

One can declare an instance of type Tenum Bool {FALSE, TRUE};

It is not necessary to use enum qualifier in front of the type name

enum Bool {NO, YES}; // NO = 0, YES = 1enum Bool {NO, FALSE=0, YEP, TRUE=1, MAYBE}; // 00112enum Bool {FALSE, TRUE}; // 01


- 26 -

C to C++C to C++

Enumeration Types

enum Bool {FALSE, TRUE};

main(){

Bool found = FALSEcode

if ( TRUE == found ){

…}

}


- 27 -

C to C++C to C++

Scope Operator

The scope operator is given by the symbol

:: Operator

Used to resolve name conflicts

Access global variables

:: DOES NOT access up one level


- 28 -

C to C++C to C++

Inline Specifier

Directs the compiler to perform inline substitution of function

…… Similar to a macro

This is only a recommendation and may be only partially implemented

struct Array{

….void put (int aValue);

….};

inline void Array::put(int aValue){

….}

inline int min (int v1, int v2){

return (v1 <= v2 ? v1 : v2)}

then…

int minVal = min(I,I);

becomes

int minVal = (v1 <= v2) ? v1 : v2;


- 29 -

C to C++C to C++

Input and Output

Input and OutputSimilar to C…. These are not defined within the C++ language

I/O is provided as component of C++ Standard Library

Input or Output Data interpreted as stream of bytes

To use I/O functions … we must include <iostream>


- 30 -

C to C++C to C++

Input and Output

IO Stream OperationsSupported by

input stream …… istream, ifstream, istrstreamoutput stream …. ostream, ofstream, ostrstream

IOstream classDerived from

istreamostream

IOS

OStreamIStream

IOStream


- 31 -

C to C++C to C++

Input and Output

OStreamOutput operation … InsertionSignified by insertion operator <<

Value inserted into (output) stream

IStreamInput operation … ExtractionSignified by extraction operator >>

Value extracted from (input) stream


- 32 -

C to C++C to C++

Input and Output

Predefined Stream Objects cin

istream class object connected to standard input cout

ostream class object connected to standard output cerr

ostream class object connected to standard errorProvides unbuffered output

clogostream class object connected to standard error

Provides buffered output


- 33 -

C to C++C to C++

Input and Output

Outputcout << stuff;

Inputcin >> place to put stuff;

Can accept Any builtin data types Any complex expression that evaluates to a data type Can be overloaded to accept user defined types cin does not allocate space for stuff


- 34 -

C to C++C to C++

Output Formatting

Must include <iomanip>

PrecisionOne can alter the precision of the output

precision( )No argument returns current precision

cout.precision( );

With an argument sets the precisioncout.precision( int aPrecision );


- 35 -

C to C++C to C++

Output Formattingput (char c)

Output

Single character

cout.put(‘a’);

write (char *s, int n)

Output

n characters from string *s

char *s = “my name is”;

cout.write(s, 5)

gives my na


- 36 -

C to C++C to C++

Output Formatting

Change of baseUse manipulators

oct, dec, hex, scientific, fixed, setprecision(int n)

cout << hex;Change output base to hexcout << hex << 256

prints 100

Change will remain in effect until changed again


- 37 -

C to C++C to C++

Input Formatting

get (char c)Input single character

char a;cin.get(&a); // Enter an ‘f’cout << a; // Prints an ‘f’

read (char *s, int n)Input n bytes from stdin into memory beginning at *s

getline (char *s, int n)Input upto n characters from stdin into memory beginning at *sInsert a NULL into the buffer

copyright 2008 oxford consulting, ltd 1 october 2008 - 1 - c to c++ c++ comments can use the symbol...

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