HOW TO example: Function pointers, external / internal [C++]

main.cpp

/*
	Demonstration of how to use function pointers in classes.

	First off, a class called operationClass is defined. This can as well be extracted to a single operationClass.h file. It's included in this cpp file to give a short overview.

	operationClass is calle by the subsequent main().

	opreationClass provides a method to set its internal calculation function to squaring and one to cubing. It also provides a method to call giving an external calculation function. The three examples are given in main().

	Andreas Herten, 2.7.2013
 */
#include <iostream>

struct operationClass {
	void SetSquare() { fPrintFunc = square;};
	void SetCube() { fPrintFunc = cube;};
	void SetArbitrary(int (*func)(int)) { fPrintFunc = func;};
	int returnTransformedValue(int val) {return fPrintFunc(val);};
private:
	int (*fPrintFunc)(int);

	static int square(int val) {return val*val;}; // has to be static!
	static int cube(int val) {return val*val*val;};
};

int quad(int number) {
	return number * number * number * number;
}

int main() {
	int originalValue = 5;

	operationClass * myClass = new operationClass();

	myClass->SetSquare();
	std::cout << originalValue << " squared (with in-class square function) = " << myClass->returnTransformedValue(originalValue) << std::endl;

	myClass->SetCube();
	std::cout << originalValue << " cubed (with in-class square function) = " << myClass->returnTransformedValue(originalValue) << std::endl;

	// int quadrupled = myClass->returnArbitrary(originalValue,quad);
	myClass->SetArbitrary(quad);
	std::cout << originalValue << " quadrupled (with external quad function) = " << myClass->returnTransformedValue(originalValue) << std::endl;
}