Silly question - multiplying integers

Hi,

This is a very nooob question ... and one I'm a little embarrassed to ask since I've been writing code for a few years now. When multiplying an int, it turns the result into a double. However, typecasting back into an int doesn't seem to work. Why is that the case?

For example:

int score = 5;

score = (int) score * 1.5;

The above code still returns score as a double. How can I multiply an integer by a value and then convert it back to an integer (rounding up / down ... don't really care)?

 

Code (csharp):

1.  
2. score = (int)(score * 1.5);
3.  

 

http://docs.unity3d.com/ScriptReference/Mathf.Ceil.html

http://docs.unity3d.com/ScriptReference/Mathf.Floor.html

There is also Mathf.CeilToInt and Mathf.FloorToInt but I don't know what the difference is, I guess Mathf.CeilToInt gives the result as int directly?

 

Floor and Ceil return floats whereas FloorToInt and CeilToInt return...well...integers.

 

Your result is a double because you are multiplying an integer with a double. C# will automatically convert ints to floats to doubles, but the other way around requires an explicit cast.

Remember the order of operations from algebra? C# has something similar. You can see that your cast to int is occurring *before* the multiplication.
http://msdn.microsoft.com/en-us/library/2bxt6kc4.aspx

In your original example score = (int) score * 1.5; this is what is happening.

1. Cast int to an int. (No effect)
2. Cast int to double in preparation for multiplication
3. Multiply two doubles
4. Assign that double result to score, which should result in an error since doubles will not automatically get cast to ints.

 

Got it .... thanks for the help! Really appreciate it.

 

The CeilToInt script reference page is a copy and paste of page Ceil, the same with FloorToInt, I knew more or less how it was because of their name "Ceil-To-int", but you know names can be deceiving some times...

 

The method signature at the top of the page says static int RoundToInt(float f)