//f1.cpp
#include <iostream>
using namespace std;

void f()
{
	cout<<"Inside the function ..."<<endl;
}

int main(int argc, char* argv[])
{
	f();
	return 0;
}
			

//f2.cpp
#include <iostream>
using namespace std;

void f();

int main(int argc, char* argv[])
{
	f();
	return 0;
}

void f()
{
	cout<<"Inside the function ..."<<endl;
}
		

//f3.h
#ifndef F3_H
#define F3_H
void f();
#endif
	

//util.cpp
#include <iostream>
#include "f3.h"
using namespace std;

void f()
{
	cout<<"Inside the function ..."<<endl;
}
	

//f3.cpp
#include <iostream>
#include "f3.h"
using namespace std;

int main(int argc, char* argv[])
{
	f();
	return 0;
}
	

#include <iostream>
using namespace std;

void increase(int n)
{
	n++;
}

int main(int argc, char* argv[])
{
	int n = 0;

	increase(n);

	cout<<n<<endl; // 0

	return 0;
}
			

#include <iostream>
using namespace std;

void increase(int &n)
{
	n++;
}

int main(int argc, char* argv[])
{
	int n = 0;

	increase(n);

	cout<<n<<endl; // 1

	return 0;
}
			

#include <iostream>
using namespace std;

int increase(int n)
{
	return ++n;
}

int main(int argc, char* argv[])
{
	int n = 0;

	n = increase(n);

	cout<<n<<endl; // 1

	return 0;
}
			

• Static local variables are not destroyed when a function returns.
• Exist for the lifetime of the program, even though their scope is only the function in which they are defined

#include <iostream>
using namespace std;

void showStatic();

int main(int argc, char *argv[])
{
	for(int i = 0; i < 10; i++)
		showStatic();

	return 0;
}

void showStatic()
{
	static int count = 0;

	count++;

	cout<<"Have been called "<<count<<" times ..."<<endl;
}
			

• The default arguments are listed in the funciton prototype, or in the function header, but not in both
• When a function uses a mixture of parameters with and without default arguments, the parameters with default arguments must be defined last

#include <iostream>
using namespace std;

int showNum(int, int = 2, int = 3);
//int showNum(int, int = 2, int);//Illegal

int main(int argc, char *argv[])
{
	showNum(10, 100, 1000);
	showNum(10, 100);
	showNum(10);
	//showNum(, 10);//Illegal

	return 0;
}

int showNum(int num1, int num2, int num3)
{
	cout<<num1<<" "<<num2<<" "<<num3<<endl;
}
			

To create a variadic function, an ellipsis (...) must be placed at the end if a parameter list

#include <iostream>
#include <cstdarg>
#include <string>
using namespace std;

void display(string p, int n, ...);

int main(int argc, char *argv[])
{
	display("Two parameters", 2, 10, 100);
	display("Four parameters", 4, 1, 2, 3, 4);

	return 0;
}

void display(string p, int n, ...)
{
	va_list l;
	va_start(l, n);

	cout<<"n: "<<n<<endl;

	for(int i = 0; i < n; i++)
		cout<<va_arg(l, int)<<endl;

	va_end(l);
}
			

//C++ 11
//g++ -std=c++11 f10.cpp
#include <iostream>
#include <vector>
#include <initializer_list>
using namespace std;

void display(const initializer_list<int> &v)
{
	for(int i = 0; i < v.size(); i++)
		cout<<v.begin()[i]<<endl;//std::initializer_list does not have subscript operator
}

int main(int argc, char *argv[])
{
	display({1, 2, 3, 4});

	return 0;
}
		

• Assign the same name to multiple functions, as long as their parameter lists are different
• Function signature
  • the name of the function and the data types of the function's parameters in the proper order
  • the function's return value is not part of the signature
  • the number of parameters is also convenient for overloading

#include <iostream>
using namespace std;

void display(int n);
void display(int n1, int n2);
void display(double n);
void display(double n1, int n2);

int main(int argc, char *argv[])
{
	int a = 1, b = 2;
	double pi = 3.14;

	display(a);
	display(a, b);
	display(pi);
	display(pi, a);

	return 0;
}

void display(int n) {cout<<n<<endl;}
void display(double n) {cout<<n<<endl;}
void display(int n1, int n2)
{
	cout<<n1<<" "<<n2<<endl;
}
void display(double n1, int n2)
{
	cout<<n1<<" "<<n2<<endl;
}
			

#include <iostream>

int factorial(int);

int main(int argc, char *argv[])
{
	std::cout<<factorial(10)<<std::endl;

	return 0;
}

int factorial(int n)
{
	if (n == 0)
		return 1;
	else
		return n*factorial(n-1);
}
			

#include <iostream>

int gcd(int x, int y);

int main(int argc, char *argv[])
{
	std::cout<<gcd(10, 2)<<std::endl;
	std::cout<<gcd(2, 10)<<std::endl;

	return 0;
}

int gcd(int x, int y)
{
	if (x % y == 0)
		return y;
	else
		return gcd(y, x % y);
}
		

• Inine functions should be in header files
• What is C++ inline functions
• Inline function FAQ

#include <iostream>

int doubleNum(int n);

int main(int argc, char *argv[])
{
	std::cout<<doubleNum(10)<<std::endl;

	return 0;
}

inline int doubleNum(int n)
{
	return 2*n;
}
			

//util.cpp
#ifndef UTIL_H
#define UTIL_H

inline int doubleNum(int n)
{
	return 2*n;
}

#endif
		

//main.cpp
#include <iostream>
#include "util.h"

int main(int argc, char *argv[])
{
	std::cout<<doubleNum(10)<<std::endl;

	return 0;
}
		

//pass by value
#include <iostream>

template <class T>
T getSquare(T);

int main(int argc, char *argv[])
{
	std::cout<<getSquare(10)<<std::endl;

	return 0;
}

template <class T>
T getSquare(T n)
{
	return n*n;
}
	

//pass by reference
#include <iostream>

template <class T>
void swap(T &, T &);

int main(int argc, char *argv[])
{
	int a = 10, b = 100;

	swap(a, b);

	std::cout<<a<<" "<<b<<std::endl;

	return 0;
}

template <class T>
void swap(T &a, T &b)
{
	T temp;
	temp = a;
	a = b;
	b = temp;
}
	

//multiple data types
#include <iostream>

template <class T1, class T2>
T1 mul(const T1 &, const T2 &);

int main(int argc, char *argv[])
{
	int a = 10;
	double b = 100.0;

	std::cout<<mul(a, b)<<std::endl;

	return 0;
}

template <class T1, class T2>
T1 mul(const T1 &a, const T2 &b)
{
	return a*b;
}

#include <iostream>

template <class T>
void message();

int main(int argc, char *argv[])
{
	message<int>();

	return 0;
}

template <class T>
void message()
{
	T a;
	std::cin>>a;
	std::cout<<a<<std::endl;
}

Explicitly select function template

• The template parameter T does not appear in the function's parameter list
• Forece the actualarguments to be promoted before the compiler deduces the template type

//deal with different data types
#include <iostream>
#include <typeinfo>
#include <string>

template <class T>
std::string getType(const T &n);

int main(int argc, char *argv[])
{
	int a = 10;
	double b = 3.14;

	std::cout<<getType(a)<<std::endl;
	std::cout<<getType(b)<<std::endl;

	return 0;
}

template <class T>
std::string getType(const T & n)
{
	char t = typeid(n).name()[0];

	switch(t)
	{
		case 'i':
			return "Integer";
			break;
		case 'd':
			return "Double";
			break;
		default:
			return "Unknown";
	}
}
	

Put the template function in .h file

//util.h
#ifndef UTIL_H
#define UTIL_H

template <class T>
int getSize(T n)
{
	return sizeof(n);
}

#endif

//main.cpp
#include <iostream>
#include "util.h"

int main(int argc, char *argv[])
{
	int a = 0;

	std::cout<<getSize(a)<<std::endl;

	return 0;
}

Put the prototype of the template in .h file and the declaration of the template function in .cpp file

• Create a template prototype with specific data type
• Include both *.h file and *.cpp file
• include *.cpp file in *.h file

//util.h
#ifndef UTIL_H
#define UTIL_H

template <class T>
int getSize(T n);

#endif

//util.cpp
#include "util.h"

template <class T>
int getSize(T n)
{
	return sizeof(n);
}

template int getSize<int>(int);
template int getSize<double>(double);

//main.cpp
#include <iostream>
#include "util.h"

int main(int argc, char *argv[])
{
	double a = 0;
	int b = 10;

	std::cout<<getSize(a)<<std::endl;
	std::cout<<getSize(b)<<std::endl;

	return 0;
}

//util.h
#ifndef UTIL_H
#define UTIL_H

template <class T>
int getSize(T n);

#endif

//util.cpp
#include "util.h"

template <class T>
int getSize(T n)
{
	return sizeof(n);
}

//main.cpp
#include <iostream>
#include "util.h"
#include "util.cpp"

int main(int argc, char *argv[])
{
	double a = 0;
	int b = 10;

	std::cout<<getSize(a)<<std::endl;
	std::cout<<getSize(b)<<std::endl;

	return 0;
}

//util.h
#ifndef UTIL_H
#define UTIL_H

template <class T>
int getSize(T n);

#include "util.cpp"

#endif

//util.cpp
template <class T>
int getSize(T n)
{
	return sizeof(n);
}

//main.cpp
#include <iostream>
#include "util.h"

int main(int argc, char *argv[])
{
	double a = 0;
	int b = 10;

	std::cout<<getSize(a)<<std::endl;
	std::cout<<getSize(b)<<std::endl;

	return 0;
}

• Template FAQ
• Define template in a .h file and implet it in a .cpp file

• Starting out with C++, Tony Gaddis
• isocpp.org