Implicit type conversion rules in C++ operators

Question

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 + fl         


        

Answer 1

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 =>