14_volumeFunction : CSCI 261 Programming Concepts (C++)

Homework 14: Volume Function (and friends)

This assignments exercises your ability to define your own functions and use them.

Concepts

Focus on one main concept for this assignment: how functions are like "mini-programs" that you can define and use.

Common C++ Library Functions

Remember in 07_rockPaperScissors how you were required to convert a letter from lower case to upper case (or vice-versa)? Your implementation was a critical exercise in learning something about char variables, but you should have asked yourself, "Surely, some genius somewhere has come across this problem before and has solved it? How can I leverage the work that they have done?"

In this case, you could have used a C++ library function called toupper.

char player1;
// ...
cin >> player1;
player1 = toupper(player1);

There are many "standard" functions in a handful of typical C++ libraries. While you won't be tested on knowing them all, you should be familiar with them since they tend to take care of common programming tasks. For example, what do the cctype library functions tolower and isalnum do?

Defining Your Own Functions

As covered in lecture, there are multiple ways to define your own functions. For now, focus on the style of "defining functions above main." For example:

#include <iostream>
using namespace std;

// Returns the sum of x and y.
int plus(int x, int y) {
    return x + y;
}

int main() {
    int a = 2, b = 3;
    cout << plus(4, 5);
    cout << plus(a, b);
    return 0;
}

Notice how we defined what "plus" is by defining the function implementation for plus above main. Notice how, in main, we used the function plus, passing it the necessary arguments it needs in order for it to do what it needs to do (sum two numbers and return the result).

Instructions

Rewrite the typical "sphere volume" assignment using library functions and a user-defined function called sphereVolume. An example interaction will look like this:

Hello, I will calculate the volume of a sphere if you tell me the radius.
Enter the radius of a sphere: 3
The volume of a sphere with radius 3 is 113.097 units cubed.
Whooopee!

Your program must:

Use the cmath library's acos function to initialize the value of a double constant called PI.
Use the cmath library's pow function to cube the radius.
Define a function called sphereVolume that accepts one integer parameter called radius and returns a double value equal to the volume of a sphere with radius radius.

Remember that in order to use the library functions acos and pow, you must include the cmath library.

Requirements and Rubric

A friendly message from The Terminator, our grading program

*bzzzt* Hel-lo. It's lonely being a cyborg. Can we be friends?

Your program must use the acos function to initialize a value for PI.

Your program must use the pow function to calculate the volume of a sphere.

Your program must define a function called sphereVolume according to the requirements.

Your main subroutine must use your sphereVolume function.

Your program must prompt the user for input only once.

Your program must print the line "The volume of a sphere with radius R is V units cubed" where R is an integer and V is a decimal number representing the volume of a sphere with radius R.

Your program must terminate after printing the above line.

It is a *bzzzt* pleasure serving you. Please come again.

This work is worth 50 points.

Requirement	Points	Notes
Place your name in the comment header in main.cpp	2
Uses `acos` to initialize a value for `PI`	5
Uses `pow` when calculating volume.	5
Correct implementation of `sphereVolume` function above `main`	15
Meaningful comment for `sphereVolume` function	3
Uses the `sphereVolume` function to calculate volume	5
Correct input prompt	5
Correct output prompt	5
Correctly calculates volume of sphere	5

Concepts Exercised: defining functions, calling functions, libraries, declaring facts.

CSCI 261 Programming Concepts (C++)