Question

Possible Duplicate:
Integer summing blues, short += short problem

I feel dumb that this is happening, but I have never had this happen before. I am trying to do the following:

foreach (short a in answers)
{
     if (a != myConstants.NOTCOMPLETE_SHORT)
     {
         result = result + a;
     }
     else
     {
         empty = true;
         break;
     }
}

answers is an array of shorts. intellisense is telling me that result + a is an int and I can’t assign it to a short.

I have to be missing something very fundamental here but not allowing two shorts to be added together and assigned to a short variable just seems weird.

Answer 1

Since a short is a 16bit Integer, if you added, say, 32,000 and 32,000 (both valid shorts), you’d get 64,000 which is not a valid short as Int16.MaxValue is 32767.

Thus, the addition operator must return a 32bit Int to prevent the result from possibly overflowing.

UPDATE:

For fun, I just tried this in PowerShell:

PS C:\> ([System.Int32]::MaxValue + [System.Int32]::MaxValue).GetType().Name
Double

PS C:\> (10000000 + 10000000).GetType().Name
Int32

So looks like an Int32 can cast to a Double if needed.

I’m gonna go out on a limb and say bounds checking during addition is more expensive, and thus should only be done if there’s a likely chance of an overflow (like two bytes or two shorts) especially when they’re possibly using the same amount of memory anyway. I think that’s just the way the language was designed.