What are the rules governing C++ single and double precision mixed calculations?

Question

For example, these variables:

result (double)
a (double)
b (float)
c (float)
d (double)

A simple calculation:

result = a *          


        

Answer 1

The floats will be upconverted to doubles. Explicitly cast the values.

ie if you want double as your result you would write:

result = a * double( b + c ) * d;

It is ALWAYS worth being explicit. It gets round misunderstandings like this and it is INSTANTLY obvious to anyone trying to use your code exactly what you mean.