Why do I need to cast this variable?

[gers1978]

I want my probabilityofWinning variable to output a floating point number, so I have the following line of code, which works.

Note probabilityofWinning is of type double, playerWin and houseWin are both int.

probabilityOfWinning = (static_cast<double>(playerWin) / (playerWin + houseWin)) * 100;

What I want to know is why do I have to cast playerWin to get a floating point output? If I don't, and use:

probabilityOfWinning = (playerWin / (playerWin + houseWin)) * 100;

it's an int that gets assigned to probabilityOfWinning

Thanks

[Bazzy]

Because otherwise you'll have integer division which will give an integer result. It would be casted to a double implicitly but you will have a truncated result

[gers1978]

So is the way I did it correct?

[jsmith]

When the compiler sees the expression "a / b" where "a" and "b" are expressions or terms of type int,
the division is performed using integer division, regardless of what the result is assigned to.