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Function pointers

////////////////////////////////////////////////////////////////////////////

on class manageFunctionPointer.cpp

////////////////////////////////////////////////////////////////////////////

//declare a function pointer

void (*pfLoad) (void) = 0;

//assign function pointer

pfLoad = loadLevel;

////////////////////////////////////////////////////////////////////////////

on class main.cpp

////////////////////////////////////////////////////////////////////////////

//call from manageFunctionPointer.cpp

extern void (*pfLoad) (void) ;

//call function pointer

pfLoad();

#function pointer

size of array accepting a string

char name[daniel] = "daniel"; // WRONG the size is 7

#char #size

Array & Vector

Array and Pointers are like Vector and Iterators

#array #vector #pointer #iterator

extracting first 4 and last 4 digit - hashing purposes

eg. 1234567

// return first 3 digits

unsigned HashFirst3(unsigned no)

{

return no / 10000;

}

// return last 3 digits

unsigned HashFirst3(unsigned no)

{

return no % 10000;

}

p.s tagging is hashing

#hashing #extract

about C

1) dont need to #include "your other file"

2) provide function prototype in main.c

3) implement function in anotherFile.c

that all.

#c

Euclid's Greatest Common Divisor ( GCD )

#include <iostream>

//Euclid's algorithm int main() { //store 2 numbers int num1, num2;

std::cout<<"enter 1st value"<<std::endl; std::cin>> num1;

std::cout<<"enter 2nd value"<<std::endl; std::cin>> num2;

//check for smaller & bigger value int smallValue, bigValue;

if(num2 > num1) { smallValue = num1; bigValue = num2; } else { smallValue = num2; bigValue = num1; }

//do Euclid's algorithm

//get the reminder unsigned int reminder = bigValue % smallValue;

//check if reminder is 0, if not keep dividing while(reminder!=0) { bigValue = smallValue; smallValue = reminder;

reminder = bigValue % smallValue; }

//GCD is found std::cout<<"GCD is " << smallValue <<std::endl;

}

#gcd #Euclid's #Greatest Common Divisor

Tokens (compiler translation)

Keyword (reserved for compiler)

char , int, sizeof, while .... anything that turn blue in your Visual Studio.

Identifiers (Use to name things)

_myFunction() //OK!

MyFunction() // OK!

int 1myVariable // NO!

int myVariable$ // NO!

Constants (assignment with value)

int i = 1;

float f = 10.4F;

double d = 10.12;

string s = "hello world"

#tokens #keyword #identifiers #constants

Difference between int main(void) and int main()

For C standard

int main(void)

int main(int argc, char * argv[]) [this parameter allow you to access environment variable, nothing complicated :) ]

why?

int main() in C means taking unknown number of argument, not no argument at all.

void main() is BAD.

why?

just not good for assembly language stomach :(

*****

For C++ standard

int main()

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

#int main()#int main(void)

Basic layout of C program

header file

function prototypes

global variable

main program()

{

local variable

statements

}

Sample Inheritance Class

class Bulk_item : public Item_base

{ public: // redefines base version so as to implement bulk purchase discount policy double net_price(std::size_t) const; private: std::size_t min_qty; // minimum purchase for discount to apply double discount; // fractional discount to apply };

#inheritance

Operator Overloading - Sample

Point Point::operator+(const Point &rhs) const

{

Point point;

point.x_ = x_ + rhs.x_;

point.y_ = y_ + rhs.y_;

return point;

}

Point Point::operator+(double a) const

{

Point point;

point.x_ = x_ + a;

point.y_ = y_ + a;

//std::cout<< "returning x "<< point.x_<<"," << point.y_ <<std::endl;

return point;

}

Point Point::operator-(double a) const

{

Point point;

point.x_ = x_ - a;

point.y_ = y_ - a;

return point;

}

Point Point::operator*(double a) const

{

Point point;

point.x_ = x_ * a;

point.y_ = y_ * a;

return point;

}

Point Point::operator%(double a) const

{

double b = DegreesToRadians(a);

double cosA=cos(b);

double sinA=sin(b);

Point point;

point.x_ = (x_* cosA) - (y_*sinA);

point.y_ = (x_* sinA) + (y_*cosA);

if(point.x_ > -EPSILON && point.x_ < EPSILON)

{

point.x_ = 0.0;

}

if(point.y_ > -EPSILON && point.y_ < EPSILON)

{

point.y_ = 0.0;

}

return point;

}

double Point::operator-(const Point& p)

{

double dist;

double pointX= (p.x_ - x_) * (p.x_ - x_) ;

double pointY= (p.y_ - y_) * (p.y_ - y_) ;

dist = pointX + pointY;

dist = sqrt(dist);

return dist;

}

Point Point:: operator^(const Point& p)

{

Point point;

point.x_ = ((x_+p.x_)/2);

point.y_ = ((y_+p.y_)/2);

return point;

}

Point& Point::operator+=(const Point& p)

{

this->x_ +=p.x_;

this->y_ +=p.y_;

return *this;

}

Point& Point::operator+=(double a)

{

this->x_ +=a;

this->y_ +=a;

return *this;

}

Point& Point::operator++() //prefix

{

++(this->x_);

++(this->y_);

return *this;

}

Point Point::operator++(int)

{

Point point;

point.x_ = x_++;

point.y_ = y_++;

return point;

}

Point Point::operator-()

{

Point p;

p.x_ = -x_;

p.y_ = -y_;

return p;

}

std::istream& operator>>(std::istream& is, Point& p)

{

is >> p.x_;

is >> p.y_;

is.get();

return is;

}

std::ostream& operator<<(std::ostream& os, const Point& p)

{

os << "("<<p.x_ <<", "<<p.y_ << ")";

return os;

}

#operator overloading #overloading

Math links

http://www.coolmath.com/reference/polygons.html

K2019: unresolved external symbol _main referenced in function ___tmainCRTStartup

Linker ->System->subsystem, change console to windows.

happen in openGL, creating camera.

if you have @ symbol error or extern error or linking error

Go to property -> Linker -> Input -> Additional Dependencies

Edit and add this.

opengl32.lib

glu32.lib

odbc32.lib

odbccp32.lib

Happen in openGL, creating camera

#@ symbol error #extern error #linking error

Pointer & References

Pointer = Gimmi the value!

References = Gimmi the addresss !

#pointer #reference #*#&

LPCWSTR compile error

some unicode problem.

eg. (NULL, "text_error" , "text_error", NULL)

change to

eg. (NULL,TEXT("text_error"), TEXT("text_error"),NULL)

OR set the configuration setting.

Project -> Project properties ->

Configuration Properties ->General ->

Character Set -> Use Multi-Byte Character Set

#LPCWSTR #LPCWSTR compile error

unsigned int

"unsigned int" means that it can only be a POSITIVE NUMBER!

"signed int" is a default "int" which can have a negative number!

#unsigned int

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