## C++, math, area.cpp

``````/**
* @file
* @brief Implementations for the [area](https://en.wikipedia.org/wiki/Area) of
* various shapes
* @details The area of a shape is the amount of 2D space it takes up.
* All shapes have a formula to get the area of any given shape.
* These implementations support multiple return types.
*
* @author [Focusucof](https://github.com/Focusucof)
*/
#define _USE_MATH_DEFINES
#include <cassert>  /// for assert
#include <cmath>    /// for M_PI definition and pow()
#include <cmath>
#include <cstdint>   /// for uint16_t datatype
#include <iostream>  /// for IO operations

/**
* @namespace math
* @brief Mathematical algorithms
*/
namespace math {
/**
* @brief area of a [square](https://en.wikipedia.org/wiki/Square) (l * l)
* @param length is the length of the square
* @returns area of square
*/
template <typename T>
T square_area(T length) {
return length * length;
}

/**
* @brief area of a [rectangle](https://en.wikipedia.org/wiki/Rectangle) (l * w)
* @param length is the length of the rectangle
* @param width is the width of the rectangle
* @returns area of the rectangle
*/
template <typename T>
T rect_area(T length, T width) {
return length * width;
}

/**
* @brief area of a [triangle](https://en.wikipedia.org/wiki/Triangle) (b * h /
* 2)
* @param base is the length of the bottom side of the triangle
* @param height is the length of the tallest point in the triangle
* @returns area of the triangle
*/
template <typename T>
T triangle_area(T base, T height) {
return base * height / 2;
}

/**
* @brief area of a [circle](https://en.wikipedia.org/wiki/Area_of_a_circle) (pi
* * r^2)
* @param radius is the radius of the circle
* @returns area of the circle
*/
template <typename T>
T circle_area(T radius) {
return M_PI * pow(radius, 2);
}

/**
* @brief area of a [parallelogram](https://en.wikipedia.org/wiki/Parallelogram)
* (b * h)
* @param base is the length of the bottom side of the parallelogram
* @param height is the length of the tallest point in the parallelogram
* @returns area of the parallelogram
*/
template <typename T>
T parallelogram_area(T base, T height) {
return base * height;
}

/**
* @brief surface area of a [cube](https://en.wikipedia.org/wiki/Cube) ( 6 * (l
* * l))
* @param length is the length of the cube
* @returns surface area of the cube
*/
template <typename T>
T cube_surface_area(T length) {
return 6 * length * length;
}

/**
* @brief surface area of a [sphere](https://en.wikipedia.org/wiki/Sphere) ( 4 *
* pi * r^2)
* @param radius is the radius of the sphere
* @returns surface area of the sphere
*/
template <typename T>
T sphere_surface_area(T radius) {
return 4 * M_PI * pow(radius, 2);
}

/**
* @brief surface area of a [cylinder](https://en.wikipedia.org/wiki/Cylinder)
* (2 * pi * r * h + 2 * pi * r^2)
* @param radius is the radius of the cylinder
* @param height is the height of the cylinder
* @returns surface area of the cylinder
*/
template <typename T>
T cylinder_surface_area(T radius, T height) {
return 2 * M_PI * radius * height + 2 * M_PI * pow(radius, 2);
}
}  // namespace math

/**
* @brief Self-test implementations
* @returns void
*/
static void test() {
// I/O variables for testing
uint16_t int_length = 0;    // 16 bit integer length input
uint16_t int_width = 0;     // 16 bit integer width input
uint16_t int_base = 0;      // 16 bit integer base input
uint16_t int_height = 0;    // 16 bit integer height input
uint16_t int_expected = 0;  // 16 bit integer expected output
uint16_t int_area = 0;      // 16 bit integer output

float float_length = NAN;    // float length input
float float_expected = NAN;  // float expected output
float float_area = NAN;      // float output

double double_length = NAN;    // double length input
double double_width = NAN;     // double width input
double double_radius = NAN;    // double radius input
double double_height = NAN;    // double height input
double double_expected = NAN;  // double expected output
double double_area = NAN;      // double output

// 1st test
int_length = 5;
int_expected = 25;
int_area = math::square_area(int_length);

std::cout << "AREA OF A SQUARE (int)" << std::endl;
std::cout << "Input Length: " << int_length << std::endl;
std::cout << "Expected Output: " << int_expected << std::endl;
std::cout << "Output: " << int_area << std::endl;
assert(int_area == int_expected);
std::cout << "TEST PASSED" << std::endl << std::endl;

// 2nd test
float_length = 2.5;
float_expected = 6.25;
float_area = math::square_area(float_length);

std::cout << "AREA OF A SQUARE (float)" << std::endl;
std::cout << "Input Length: " << float_length << std::endl;
std::cout << "Expected Output: " << float_expected << std::endl;
std::cout << "Output: " << float_area << std::endl;
assert(float_area == float_expected);
std::cout << "TEST PASSED" << std::endl << std::endl;

// 3rd test
int_length = 4;
int_width = 7;
int_expected = 28;
int_area = math::rect_area(int_length, int_width);

std::cout << "AREA OF A RECTANGLE (int)" << std::endl;
std::cout << "Input Length: " << int_length << std::endl;
std::cout << "Input Width: " << int_width << std::endl;
std::cout << "Expected Output: " << int_expected << std::endl;
std::cout << "Output: " << int_area << std::endl;
assert(int_area == int_expected);
std::cout << "TEST PASSED" << std::endl << std::endl;

// 4th test
double_length = 2.5;
double_width = 5.7;
double_expected = 14.25;
double_area = math::rect_area(double_length, double_width);

std::cout << "AREA OF A RECTANGLE (double)" << std::endl;
std::cout << "Input Length: " << double_length << std::endl;
std::cout << "Input Width: " << double_width << std::endl;
std::cout << "Expected Output: " << double_expected << std::endl;
std::cout << "Output: " << double_area << std::endl;
assert(double_area == double_expected);
std::cout << "TEST PASSED" << std::endl << std::endl;

// 5th test
int_base = 10;
int_height = 3;
int_expected = 15;
int_area = math::triangle_area(int_base, int_height);

std::cout << "AREA OF A TRIANGLE" << std::endl;
std::cout << "Input Base: " << int_base << std::endl;
std::cout << "Input Height: " << int_height << std::endl;
std::cout << "Expected Output: " << int_expected << std::endl;
std::cout << "Output: " << int_area << std::endl;
assert(int_area == int_expected);
std::cout << "TEST PASSED" << std::endl << std::endl;

// 6th test
double_expected =
113.09733552923255;  // rounded down because the double datatype
// truncates after 14 decimal places

std::cout << "AREA OF A CIRCLE" << std::endl;
std::cout << "Input Radius: " << double_radius << std::endl;
std::cout << "Expected Output: " << double_expected << std::endl;
std::cout << "Output: " << double_area << std::endl;
assert(double_area == double_expected);
std::cout << "TEST PASSED" << std::endl << std::endl;

// 7th test
int_base = 6;
int_height = 7;
int_expected = 42;
int_area = math::parallelogram_area(int_base, int_height);

std::cout << "AREA OF A PARALLELOGRAM" << std::endl;
std::cout << "Input Base: " << int_base << std::endl;
std::cout << "Input Height: " << int_height << std::endl;
std::cout << "Expected Output: " << int_expected << std::endl;
std::cout << "Output: " << int_area << std::endl;
assert(int_area == int_expected);
std::cout << "TEST PASSED" << std::endl << std::endl;

// 8th test
double_length = 5.5;
double_expected = 181.5;
double_area = math::cube_surface_area(double_length);

std::cout << "SURFACE AREA OF A CUBE" << std::endl;
std::cout << "Input Length: " << double_length << std::endl;
std::cout << "Expected Output: " << double_expected << std::endl;
std::cout << "Output: " << double_area << std::endl;
assert(double_area == double_expected);
std::cout << "TEST PASSED" << std::endl << std::endl;

// 9th test
double_expected = 1256.6370614359172;  // rounded down because the whole
// value gets truncated

std::cout << "SURFACE AREA OF A SPHERE" << std::endl;
std::cout << "Input Radius: " << double_radius << std::endl;
std::cout << "Expected Output: " << double_expected << std::endl;
std::cout << "Output: " << double_area << std::endl;
assert(double_area == double_expected);
std::cout << "TEST PASSED" << std::endl << std::endl;

// 10th test
double_height = 7.0;
double_expected = 276.46015351590177;
double_area = math::cylinder_surface_area(double_radius, double_height);

std::cout << "SURFACE AREA OF A CYLINDER" << std::endl;
std::cout << "Input Radius: " << double_radius << std::endl;
std::cout << "Input Height: " << double_height << std::endl;
std::cout << "Expected Output: " << double_expected << std::endl;
std::cout << "Output: " << double_area << std::endl;
assert(double_area == double_expected);
std::cout << "TEST PASSED" << std::endl << std::endl;
}

/**
* @brief Main function
* @returns 0 on exit
*/
int main() {
test();  // run self-test implementations
return 0;
}
``````