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Subject: Re: Sign of Integer Operands: int vs unsigned int

Author: Bo Persson

Date: 04:54:19 09/28/03

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On September 27, 2003 at 09:36:00, Russell Reagan wrote:

>On September 27, 2003 at 08:22:47, Omid David Tabibi wrote:
>
>>Isn't it better to always use unsigned int instead of int, for example:
>>
>>    for (unsigned int i; i < numner; i++)
>>
>>instead of
>>
>>    for (int i; i < numner; i++)
>
>You could test it pretty easy. I have something in my program like this:
>
>typedef int Int32;
>typedef unsigned int UInt32;
>typedef Int32 Int;
>typedef Uint32 UInt;
>
>There are others for 16-bit and 8-bit data. The main advantage is that I can
>switch to a 64-bit platform by changing a line or two of code here
>(specifically, Int and UInt to be 64-bit types).
>
>I could add a FastInt type or something like that, which will just be the
>fastest available type when there is a choice between int and unsigned int. You
>could do two compiles and compare.
>
>Also worth checking out is this chart
>(http://www.tantalon.com/pete/cppopt/appendix.htm#AppendixB_RelativeCosts),
>although it is on a PIII. Note that the author says statistical error is +/-
>0.1. It would be interesting to see how the author tested this.

Yes. Also considering that the other table "STL Container Efficiency" contains a
number of factual errors, the value of this table can be questioned.

>
>Also, is there a penalty for doing assignment between int and unsigned, and vice
>versa? It seems like some kind of conversion might be needed.

No, not if the values are of the same size.


Bo Persson





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