Calculating volume for sphere in C++

开发者_JAVA技巧

This is probably an easy one, but is the right way to calculate volume for a sphere in C++? My getArea() seems to be right, but when I call getVolume() it doesn't output the right amount. With a sphere of radius = 1, it gives me the answer of pi, which is incorrect:

double Sphere::getArea() const
{
    return 4 * Shape::pi * pow(getZ(), 2);
}

double Sphere::getVolume() const
{
    return (4 / 3) * Shape::pi * pow(getZ(), 3);
}

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You're using integer division in (4 / 3). Instead, use floating point division: (4.0 / 3.0).

4/3 is 1, because integer division only produces integers. You can confirm this by test code: std::cout << (4/3) << std::endl;.

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In (4 / 3), these are both integers so you get integer division. That means the result will be truncated (1.333... becomes 1). Make one of them a double so the other gets promoted to a double during division, yielding a correct result.

I prefer to use (4.0 / 3.0).

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(4 / 3) is an integer expression and is therefore being truncated to 1. Try (4.0 / 3.0)