3.17. Activecode Exercises

Answer the following Activecode questions to assess what you have learned in this chapter.

Fix the errors in the code below so that it returns the area of a circle with radius r. Use cmath functions to get an accurate value for pi.

double area(int r) { constexpr double pi = sin(1.0); double area = pi * r ^ 2; return area; } ==== #include <functional> #include <iomanip> #include <iostream> #include <string> template <class T, class Compare = std::equal_to<T>> void check (const std::string& name, const T& actual, const T& expected, const Compare& op = Compare()) { std::cout << std::left << std::setfill('.') << std::setw(50) << name << std::setw(7) << std::left; if(op(actual, expected)) { std::cout << " OK \n"; return; } std::cout << " FAILED\n"; std::cout << "\treceived [" << std::boolalpha << actual << "], but expected [" << expected << "]\n"; exit(1); } bool close_to(double x, double y) { return std::abs(x-y) < 0.001; } int main() { check("radius == 5", area(5), 78.5398, close_to); check("radius == 7.5", area(7.5), 176.715, close_to); }

Below is one way to fix the program. C++ doesn’t use the ^ operator for exponents. We can get the square of r by multiplying it by itself.

#include <cmath> double area(double r) { constexpr double pi = 4*atan(1.0); double area = pi * r * r; return area; } ==== #include <functional> #include <iomanip> #include <iostream> #include <string> template <class T, class Compare = std::equal_to<T>> void check (const std::string& name, const T& actual, const T& expected, const Compare& op = Compare()) { std::cout << std::left << std::setfill('.') << std::setw(50) << name << std::setw(7) << std::left; if(op(actual, expected)) { std::cout << " OK \n"; return; } std::cout << " FAILED\n"; std::cout << "\treceived [" << std::boolalpha << actual << "], but expected [" << expected << "]\n"; exit(1); } bool close_to(double x, double y) { return std::abs(x-y) < 0.001; } int main() { check("radius == 5", area(5), 78.5398, close_to); check("radius == 7.5", area(7.5), 176.715, close_to); }

Fix the code below so that it prints “2 elephants”.

#include <iostream> using namespace std; void printAnimals(string a, int b) { cout << b << a; } int main () { // DO NOT MODIFY ANYTHING BELOW THIS LINE printAnimals(2, "elephants"); }

Fix the code below so that it prints 12 / 8 = 1.5.

#include <iostream> void divide (int a, int b) { cout << a / b; } int main () { int a = 8; int b = 12; // DO NOT MODIFY ANYTHING BELOW THIS LINE cout << b << " / " << a << " = "; divide (a, b); }

Below is one way to fix the program. It’s crucial that you input your arguments in the correct order so as to avoid a semantic error. Also, it’s important that you understand that when you divide two integers… you will get an integer as a result.

#include <iostream> void divide (double a, double b) { std::cout << a / b; } int main () { int a = 8; int b = 12; std::cout << b << " / " << a << " = "; divide (b, a); }

Finish the code below so that it calculates the common log of a minus the natural log of a and returns the difference. You will need to use cmath functions.

double log_subtract (double a) { return difference; } int main () { // DO NOT MODIFY ANYTHING BELOW THIS LINE cout << "Testing with a = 8..." << endl; cout << " Your solution has difference = "; logSubtraction(8); cout << endl; cout << " The correct solution has difference = -1.17635" << endl; cout << "Testing with a = -2..." << endl; cout << " Your solution has difference = "; logSubtraction(-2); cout << endl; cout << " The correct solution has difference = nan"; } ==== #include <functional> #include <iomanip> #include <iostream> #include <string> template <class T, class Compare = std::equal_to<T>> void check (const std::string& name, const T& actual, const T& expected, const Compare& op = Compare()) { std::cout << std::left << std::setfill('.') << std::setw(50) << name << std::setw(7) << std::left; if(op(actual, expected)) { std::cout << " OK \n"; return; } std::cout << " FAILED\n"; std::cout << "\treceived [" << std::boolalpha << actual << "], but expected [" << expected << "]\n"; exit(1); } bool close_to(double x, double y) { return std::abs(x-y) < 0.001; } int main() { check("test value == 8", log_subtract(8), -1.17635, close_to); check("test value == 42", log_subtract(42), -2.11442, close_to); check("test value == pi", log_subtract(3.14159), -0.64758, close_to); check("test value == 1776", log_subtract(1776), -4.23268, close_to); }

Finish the code below so that it prints “First Line”, a border, and “Second Line.” on three separate lines.

#include <iostream> using namespace std; void border () { cout << "------------\n"; } int main () { // Write some code below to call the function appropriately }

Below is one way to complete the program.

#include <iostream> using std::cout; void border () { cout << "------------\n"; } int main () { cout << "First Line.\n"; border(); cout << "Second Line.\n"; }

Write a function called int_division that takes two doubles as parameters and returns the quotient of the integer division of the first number divided by the second. Be sure to include any necessary headers.

int int_division () { return quotient; } ==== #include <functional> #include <iomanip> #include <iostream> #include <string> template <class T, class Compare = std::equal_to<T>> void check (const std::string& name, const T& actual, const T& expected, const Compare& op = Compare()) { std::cout << std::left << std::setfill('.') << std::setw(50) << name << std::setw(7) << std::left; if(op(actual, expected)) { std::cout << " OK \n"; return; } std::cout << " FAILED\n"; std::cout << "\treceived [" << std::boolalpha << actual << "], but expected [" << expected << "]\n"; exit(1); } int main() { check("test a = 2.4, b = 6.8...", int_division(2.4, 6.8), 0); check("test a = -8.6, b = 4.2...", int_division(-8.6, 4.2), -2); check("test a = 42.2, b = 11.5...", int_division(42.2, 11.5), 3); }

Write a function called gpa_boost that returns your GPA rounded up to the nearest whole value. If your GPA is already at the nearest whole value, then there is no rounding. Be sure to include any necessary headers.

double gpa_boost () { } ==== #include <functional> #include <iomanip> #include <iostream> #include <string> template <class T, class Compare = std::equal_to<T>> void check (const std::string& name, const T& actual, const T& expected, const Compare& op = Compare()) { std::cout << std::left << std::setfill('.') << std::setw(50) << name << std::setw(7) << std::left; if(op(actual, expected)) { std::cout << " OK \n"; return; } std::cout << " FAILED\n"; std::cout << "\treceived [" << std::boolalpha << actual << "], but expected [" << expected << "]\n"; exit(1); } bool close_to(double x, double y) { return std::abs(x-y) < 0.001; } int main() { check("test gpa == 2.513", gpa_boost(2.513), 3.0, close_to); check("test gpa == 4.000", gpa_boost(4.000), 4.0, close_to); check("test gpa == 2.999", gpa_boost(2.999), 3.0, close_to); check("test gpa == 3.0001", gpa_boost(3.0001), 4.0, close_to); }

Below is one way to complete the program. I used the ceil <math/ceil> function from the ``cmath` library, but you could have solved this problem without using any functions from cmath.

#include <cmath> double gpa_boost (double gpa) { return ceil(gpa); } ==== #include <functional> #include <iomanip> #include <iostream> #include <string> template <class T, class Compare = std::equal_to<T>> void check (const std::string& name, const T& actual, const T& expected, const Compare& op = Compare()) { std::cout << std::left << std::setfill('.') << std::setw(50) << name << std::setw(7) << std::left; if(op(actual, expected)) { std::cout << " OK \n"; return; } std::cout << " FAILED\n"; std::cout << "\treceived [" << std::boolalpha << actual << "], but expected [" << expected << "]\n"; exit(1); } bool close_to(double x, double y) { return std::abs(x-y) < 0.001; } int main() { check("test gpa == 2.513", gpa_boost(2.513), 3.0, close_to); check("test gpa == 4.000", gpa_boost(4.000), 4.0, close_to); check("test gpa == 2.999", gpa_boost(2.999), 3.0, close_to); check("test gpa == 3.0001", gpa_boost(3.0001), 4.0, close_to); }

Write a function called volume_prism that takes three double side-lengths as parameters, and returns the volume of a the rectangular prism. Be sure to include any necessary headers.

volume_prism (); ==== #include <functional> #include <iomanip> #include <iostream> #include <string> template <class T, class Compare = std::equal_to<T>> void check (const std::string& name, const T& actual, const T& expected, const Compare& op = Compare()) { std::cout << std::left << std::setfill('.') << std::setw(50) << name << std::setw(7) << std::left; if(op(actual, expected)) { std::cout << " OK \n"; return; } std::cout << " FAILED\n"; std::cout << "\treceived [" << std::boolalpha << actual << "], but expected [" << expected << "]\n"; exit(1); } bool close_to(double x, double y) { return std::abs(x-y) < 0.001; } int main() { check("test a = 3, b = 4, c = 5...", volume_prism(3,4,5), 60.0, close_to); check("test a = 5.7, b = 3.9, c = 1.3...", volume_prism(5.7,3.9,1.3), 28.899, close_to); }

Write a function called tan_degrees that returns the tangent of an angle given as a double in degrees. Use 3.14159 for pi. Be sure to include any necessary headers.

tan_degrees (); ==== #include <functional> #include <iomanip> #include <iostream> #include <string> template <class T, class Compare = std::equal_to<T>> void check (const std::string& name, const T& actual, const T& expected, const Compare& op = Compare()) { std::cout << std::left << std::setfill('.') << std::setw(50) << name << std::setw(7) << std::left; if(op(actual, expected)) { std::cout << " OK \n"; return; } std::cout << " FAILED\n"; std::cout << "\treceived [" << std::boolalpha << actual << "], but expected [" << expected << "]\n"; exit(1); } bool close_to(double x, double y) { return std::abs(x-y) < 0.001; } int main() { check("test 45 degrees", tan_degrees(45), 0.9992, close_to); check("test 112.1 degrees", tan_degrees(112.1), -2.4627, close_to); }

Below is one way to complete the program. You need to make sure to convert your angle to radians before doing any calculations with trigonometric functions.

#include <cmath> namespace mesa { constexpr double pi = 3.14159; double deg_to_radian (double degrees) { return degrees * (pi / 180); } } double tan_degrees (double degrees) { double radians = mesa::deg_to_radian(degrees); return tan(radians); } ==== #include <functional> #include <iomanip> #include <iostream> #include <string> template <class T, class Compare = std::equal_to<T>> void check (const std::string& name, const T& actual, const T& expected, const Compare& op = Compare()) { std::cout << std::left << std::setfill('.') << std::setw(50) << name << std::setw(7) << std::left; if(op(actual, expected)) { std::cout << " OK \n"; return; } std::cout << " FAILED\n"; std::cout << "\treceived [" << std::boolalpha << actual << "], but expected [" << expected << "]\n"; exit(1); } bool close_to(double x, double y) { return std::abs(x-y) < 0.001; } int main() { check("test 45 degrees", tan_degrees(45), 0.9992, close_to); check("test 112.1 degrees", tan_degrees(112.1), -2.4627, close_to); }

Write a function called volume_sphere that takes a double radius as a parameter and returns the volume of a sphere with the provided radius. Use 3.14159 for pi. Be sure to include any necessary headers.

volume_sphere (); ==== #include <functional> #include <iomanip> #include <iostream> #include <string> template <class T, class Compare = std::equal_to<T>> void check (const std::string& name, const T& actual, const T& expected, const Compare& op = Compare()) { std::cout << std::left << std::setfill('.') << std::setw(50) << name << std::setw(7) << std::left; if(op(actual, expected)) { std::cout << " OK \n"; return; } std::cout << " FAILED\n"; std::cout << "\treceived [" << std::boolalpha << actual << "], but expected [" << expected << "]\n"; exit(1); } bool close_to(double x, double y) { return std::abs(x-y) < 0.001; } int main() { check("test radius = 3", volume_sphere(3), 113.097, close_to); check("test radius = 3.24", volume_sphere(3.24), 142.47, close_to); }

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