Which variables should I typecast when doing math operations in C/C++?

Question

For example, when I\'m dividing two ints and want a float returned, I superstitiously write something like this:

int a = 2, b = 3;
float c = (float)a / (floa         


        

Answer 1

I think as long as you are casting just one of the two variables the compiler will behave properly (At least on the compilers that I know).

So all of:

float c = (float)a / b;

float c = a / (float)b;

float c = (float)a / (float)b;

will have the same result.

Answer 2

Having worked on safety-critical systems, i tend to be paranoid and always cast both factors: float(a)/float(b) - just in case some subtle gotcha is planning to bite me later. No matter how good the compiler is said to be, no matter how well-defined the details are in the official language specs. Paranoia: a programmer's best friend!

Answer 3

Then there are older brain-damaged types like me who, having to use old-fashioned languages, just unthinkingly write stuff like

int a;
int b;
float z;

z = a*1.0*b;

Of course this isn't universal, good only for pretty much just this case.