Volume of a Sphere- Need Help

[CMonkey]

Hello! I am writing a program for a class I am taking, but I am stuck. The directions for the assignment are:

Write a program that (using a function and no math libraries) displays the volume of a sphere with a radius from 0 to 4.0 in .2 increments. Use float type for the return type and argument type.

The program runs fine; however, my teacher said it is incorrect because "You did not write a function for any of these programs. The result must take place in a function and be returned to main()" I'm lost.

Here is my REVISED code:

#include <iostream> //preprocessor directive

using namespace std;

float VolSphere (float r)

{
float volume;
volume = (1.33) * (3.14) * (r * r * r);
return volume;
}

int main()

{
float r = 0;
while (r <= 4)

{
cout << "Radius: " << r << " Volume: " << VolSphere (r) << endl;
r = r + .2;

}
return 0;

}

[CMonkey]

I removed the last return so the code reads:

{
cout << "Radius: " << r <<" Volume: " << VolSphere (r) << endl;
r + .2;
return 0;
}


}


The program now stops after one line, but I am still getting "0" for both radius and volume.

[wildblue]

r + .2;

This adds the value .2 and whatever is in r, but doesn't actually update the value in r. You need an assignment statement.

Edit - the return statement ending the main function shouldn't be in the while loop.

[AIa43]

This adds .2 to r, but doesn't actually update the value in r. You need an assignment statement.

An assignment statement is something such as:

r = r + .2
I think so, at least.

Otherwise, make a for statement, with syntax and example as follows:

for (iterator; conditional; increment)
{
//do stuff until the conditional isn't met.
}

for (double something; something < 10; something = something + 1)
{
//do stuff
}

[CMonkey]

I have tried adding "r =" in front of "r + .2" but I still get the same thing. I'm not sure where else to assign r.

[CMonkey]

I added back the "r=r+.2" statement and moved the return statement as you all suggested, and it works! Thank you!!

[Chervil]

float r = 0;
while (r <= 4)
{
    cout << "Radius: " << r <<" Volume: " << VolSphere (r) << endl;
    r += .2;
}

note the += operator.
that's a shorter way of writing

    r = r + .2;

[CMonkey]

I submitted the assignment to my teacher, but he returned it saying that I did not write a function. I need to write a function that returns to main. I am lost. What do I need to do?

[keskiverto]

http://www.cplusplus.com/doc/tutorial/functions/

However, VolSphere is a function (that takes a float and returns a float, as requested). Ask your teacher what the VolSphere is.

[z05DSL3A]

What was the code you handed in?

I need to write a function that returns to main. I am lost. What do I need to do?

He might mean that he wants the value returned from VolSphere(r) to be assigned to a variable in main before printing the variable to the screen.

[CMonkey]

@Grey Wolf-

The code I handed in:

#include <iostream> //preprocessor directive

using namespace std;

float VolSphere (float r)

{
float volume;
volume = (1.33) * (3.14) * (r * r * r);
return volume;
}

int main()

{
float r = 0;
while (r <= 4)

{
cout << "Radius: " << r << " Volume: " << VolSphere (r) << endl;
r = r + .2;

}
return 0;

}

[Chervil]

I submitted the assignment to my teacher, but he returned it saying that I did not write a function. I need to write a function that returns to main.

If that is all he said, then he was mistaken.

You did write a function, and it does return to main.

[CMonkey]

@Chervil- That's what I thought :S

[z05DSL3A]

I would say that he does want you to return the value to a local variable and then display the result. Try it but keep an eye on 0.0 and 4.0.

[dhayden]

Also, you should try to make the formula more accurate. 1.33 is only sort of close to 4/3 and 3.14 is only sort of close to pi.

If you #include <math.h> then you may be able to use the constant M_PI. So the formula would become 4.0/3.0*M_PI*r*r*r. Note that it's 4.0/3.0, not 4/3. Since 4 and 3 are integers, 4/3 is 1.