adding Variables of different types in C

Question

float + (short)long = ?

I am adding these types and based on my calculation I am getting a float as an answer but the right answer is double. can anyone give me an example of how it becomes double or explanation..

Answer 1

Operators that take two arithmetic operands in C always require both operands to be of the same type. If they aren't, then one or both are converted according to the usual arithmetic conversions, which are fully described in section 6.3.1.8 of the C standard (the link is to a draft of the 2011 standard).

Briefly:

• If either operand is of type long double, the other is converted to long double.
• Otherwise, if either operand is of type double, the other is converted to `double.
• Otherwise, if either operand is of type float, the other is converted to float.

This is followed by a set of rules for two operands of integer type, which don't apply in this case.

If you need a double result, you need to convert one or both operands to double. If you convert just one of them, it will cause the other to be converted as well. (You might want to convert both just to be explicit.)

For example, if you have:

float f;
long n;
double x = f + n;

then the result of the addition is float, which is converted to double only after the addition is performed. To do a double multiplication, change the last line to:

double x = (double)f + (double)n;

On the other hand, if you want a double result, it's very likely that your float operand should have been declared as a double in the first place. double is in some sense the "default" floating-point type in C (it's the type of unsuffixed literals like 1.0, for example). float is used mostly when it's important to save memory space, such as when you have very large arrays. On many systems, float arithmetic isn't even any faster than double arithmetic (though I'm not 100% sure on that last point).

Answer 2

try to do:

float F;
short L;
double res = (double)(F + L);