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C++ Examples for Understanding the C Preprocessor

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tianxiasoft 13

published 4 years ago

#include <iostream>

using namespace std;

/*  This is an example that calculates the length and area of circle   				  */

// Define PI. If it is already defined, undefine it
#ifdef PI
#undef PI
#define PI						3.141592

// Define macro that calculates the x * x
#define SQR(x)					(x * x)
// Define macro that calculates the length of a circle.
#define LengthOfCircle(r)		(2 * PI * r)
// Define macro that calculates the area of a circle.
#define AreaOfCircle(r)			(PI * SQR(r))

// main function
int main()
	// input radius
	float radius;
	cout << "Input the radius of circle : ";
	cin >> radius;

	// print length and area of the circle of radius
	cout << "Length is " << LengthOfCircle(radius) << endl;
	cout << "Area is " << AreaOfCircle(radius) << endl;

	// wait for any key pressing
	return 0;
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