objective c float values

Question

Why we can not store the division result of two integers into the float variable ?

int a = 100;
int b =50;
float temp = b/a;

it gives t= 0 !

also i did

int temp = b/a;

it gives t= 0 !

but when I did

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

it gives proper result. Why so ?

Answer 1

The reason why float temp = b/a; gives 0 while float temp = (float)b/a; gives 0.5 is that the compiler determines the output type of the division operation based upon the types of the operands, not the destination storage type. Put simply:

int   /   int = int
float /   int = float
int   / float = float
float / float = float

So when you do float temp = b/a; you're doing in integer divide of b and a, and then storing the resulting integer (0 in your example) into a variable of type float. In essence, by the time the value is converted to floating-point you have already lost the information you are looking for (assuming you wanted to do a floating-point divide), and the conversion is not going to bring it back.

In order to get the result you want (again, assuming that you want to do a floating-point divide), you need to cast at least one of the operands to float before you divide.