I always come across code that uses int for things like .Count, etc, even in the framework classes, instead of uint.
What's the reason for this?
views:
453answers:
7
+10
A:
int, in c, is specifically defined to be the default integer type of the processor, and is therefore held to be the fastest for general numeric operations.
Adam Davis
2009-04-23 16:58:10
Thanks Adam, I actually need the extra range of the uint, but do you think using it would degrade my app's performance?
Joan Venge
2009-04-23 17:00:05
In modern processors no, unsigned int and signed int should be about the same. If there's a difference it's marginal, and if you need every last ounce of performance it's worth benchmarking for your particular compiler/OS/CPU/etc.
Adam Davis
2009-04-23 17:01:05
No, it would not change the performance of your program. To get answers like this, a microbenchmark is your friend (I recommend MeasureIt). *On my computer* adding uints seems to perform about 20% faster than ints (although measurements this small aren't too reliable). In general worrying about this would be considered optimizing prematurely; use whatever suits the situation best and optimize it later if it causes a _measurable_ performance impact.
Eric Burnett
2009-04-23 20:39:04
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A:
UInt32 is not CLS compliant so it might not be available in all languages that target the Common Language Specification. Int32 is CLS compliant and therefore is guaranteed to exist in all languages.
dtb
2009-04-23 16:58:53
But why would this affect whether a person codes in a particular language with Int32? If language X doesn't accept it, but language Y does, why would I care about X if I'm programming in Y? Is it just for examples which are implemented in many languages to show off features, or is there some other reason why I should program in Y with the restrictions in X?
Adam Davis
2009-04-23 17:14:51
The idea of the Common Language Specification is that you can have a single Base Class Library for all languages. If the BCL only uses CLS compliant features and all languages support all CLS compliant features, then the BCL can be used from all languages. The same applies to your class libraries if you want them to be usable from other languages than it was written in.
dtb
2009-04-23 17:24:00
@Adam: there's nothing that says that your code must conform to only what the BCL provides. Howewer, the BCL is intended to be consumable by any CLS compliant assembly, so the BCL must restrict itself to CLS features.
Michael Burr
2009-04-23 17:45:34
A:
Some old libraries and even InStr use negative numbers to mean special cases. I believe either its laziness or there's negative special values.
Daniel A. White
2009-04-23 16:59:07
+1
A:
Some things use int so that they can return -1 as if it were "null" or something like that. Like a ComboBox will return -1 for it's SelectedIndex if it doesn't have any item selected.
Max Schmeling
2009-04-23 16:59:35
A:
Another reason for using int:
Say you have a for-loop like this:
for (i = 0; i <= someList.Count - 1; i++) {
// Stuff
}
(though you probably shouldn't do it that way)
obviously, if someList.Count was 0 and unsigned, you would have a problem.
Botz3000
2009-04-23 17:05:44
because someList's indices are zero-based. I'd rather use (i < Count) or foreach, but you get the point. Instead of an overflow i'd rather have a negative value which doesn't hurt in that case.
Botz3000
2009-04-23 18:13:36
I see, but I personally never seen people using <= in for loops, since indices start from 0.
Joan Venge
2009-04-23 19:11:02
Me neither. Hmm, let's look at it this way:for (i = list.Count - 1; i >= 0; i--)for starting from the end of the list. not that uncommon.
Botz3000
2009-04-23 20:12:14
+1
A:
If the number is truly unsigned by its' intrinsic nature then I would declare it an unsigned int. However, if I just happen to be using a number (for the time being) in the positive range then I would call it an int. The main reasons being that:
- It avoids having to do a lot of type-casting as most methods/functions are written to take an int and not an unsigned int.
- It eliminates possible truncation warnings.
- You invariably end up wishing you could assign a negative value to the number that you had originally thought would always be positive.
Are just a few quick thoughts that came to mind.
I used to try and be very careful and choose the proper unsigned/signed and I finally realized that it doesn't really result in a positive benefit. It just creates extra work. So why make things hard by mixing and matching.
Dunk
2009-04-23 17:14:53
+1
A:
UInt32 isn't CLS-Compliant. http://msdn.microsoft.com/en-us/library/system.uint32.aspx
I think that over the years people have come to the conclusions that using unsigned types doesn't really offer that much benefit. The better question is what would you gain by making Count a UInt32?
Mark Knudson
2009-04-23 20:54:46