Does an impure function return anything?

Question

An impure function does not return anything. That is what my computer textbook says. I am not sure it is correct as by definition an impure function is a function which changes the state of the parameters passed to it. The parameter is generally an object.

eg:

void impurefunc(Class object)
{
   object.var = 9; //object's variable changed
}

If it returns anything does it remain impure?

Answer 1

An impure function does not return anything. That is what a computer textbook says.

It's wrong. An impure function can indeed return anything after doing whatever impure things it does. This is true in Java and every other language I know of.