Implicit type conversion rules in C++ operators
I want to be better about knowing when I should cast. What are the implicit type conversion rules in C++ when adding, multiplying, etc. For example,
int + float = ?
int * float = ?
float * int = ?
int / float = ?
float / int = ?
int / int = ?
int ^ float = ?
et cetera...
Will the expression always be evaluated as the more precise type? Do the rules differ for Java? Please correct me if I have worded this question inaccurately.
Answer
In C++ operators (for POD types) always act on objects of the same type.
Thus if they are not the same one will be promoted to match the other.
The type of the result of the operation is the same as operands (after conversion).
If either is long double the other is promoted to long double
If either is double the other is promoted to double
If either is float the other is promoted to float
If either is long long unsigned int the other is promoted to long long unsigned int
If either is long long int the other is promoted to long long int
If either is long unsigned int the other is promoted to long unsigned int
If either is long int the other is promoted to long int
If either is unsigned int the other is promoted to unsigned int
If either is int the other is promoted to int
Both operands are promoted to int
Note. The minimum size of operations is int. So short/char are promoted to int before the operation is done.
In all your expressions the int is promoted to a float before the operation is performed. The result of the operation is a float.
int + float => float + float = float
int * float => float * float = float
float * int => float * float = float
int / float => float / float = float
float / int => float / float = float
int / int = int
int ^ float => <compiler error>