Avoiding Errors during Math Operations <vb.net>

[NeuralJack]

I have been told a few times that the best thing to do when programming is to try to avoid raising any and all potential errors, instead of using the raised errors themselves to figure out what to do next. At least, this is what I took from it.

So, I'm wondering if you guys think this should be done during simple math calculations too.. in order to avoid things like overflow? Do you check each and every math operation you do before you do it, or do you let the try/catch handle an error the way you want it?

 

Simple Case:

You want to add 2 user entered Integers together. If there is an overflow set the Total to Maximum Int 64 Value.

 

Addition Method 1 (Use Try/Catch)

Dim Int1 As Int64 = 'User enters a value
Dim Int2 As Int64 = 'User enters a value
Dim Total As Int64

Try
    Total = Int1 + Int2
Catch ex1 as System.OverflowException
    Total = Int64.MaxValue
End Try

 

Addition Method 2 (Check for overflow yourself before addition, to avoid raising errors)

Private Sub AddThis()
Dim Int1 As Int64 = 'User enters a value
Dim Int2 As Int64 = 'User enters a value
Dim Total As Int64

If AdditionIsOK()
   Total = Int1 + Int2
Else 
   Total = int64.MaxValue
End If
End Sub

Private Function AdditionIsOK(ByVal Int1 as int64,ByVal  Int2 as int64) as boolean
  If Int1 >= 0 And Int2 >= 0 Then  'Both Numbers are Positive
       Dim MaxAllowedInt2 as int64 = Int64.MaxValue - Int1
       If Int2 <= MaxAllowedInt2
            Return True
       EndIf

  ElseIf  ... 'Code for when Both Numbers are Negative
  ElseIf  ... 'Code for when Int1 is Negative and Int2 is Positive
  ElseIf  ... 'Code for when Int2 is Negative and Int1 is Positive

  EndIf

Return False

End Function

 

I don't know, Method 2 just seems a little excessive to me. But you guys have slapped me straight many times and I'm beggin for more. Let me know what you think.

[mskeel]

Personally, I'd go with method 1 unless it is highly probable that overflows occur a majority of the time. In my experience, an overflow is a rare event and only occurs under exceptional circumstances.

 

It's not really about trying to prevent all errors and never throwing an exception. The basic idea is that you want to capture the likely errors and reserve exceptions for exceptional errors, or things that don't happen that often.

[NeuralJack]

Ok thanks, I agree. Yes, overflows for this project should also be rare.

 

I'll try to stick with the mentality of avoiding the use of raised errors as tools(in try/catch statements), unless the chance of a raised error is extremely low.

[PlausiblyDamp]

The actual performance hit of an exception being thrown isn't that great in a release build anyway (there still is one so excessive exceptions need to be avoided) however the second example of yours probably puts it's own performance overheads on and increases the code to maintain while decreasing the readability...

 

I am a big believer in the phrase "Premature optimization is the root of all evil." if the performance hit of writing cleaner more readable and maintainable code is sufficient to be a problem then I will look at alternatives....

Edited February 24, 2007 by PlausiblyDamp