Re: What is your opinion about unsigned int u = -2 ?

On 09/08/2024 21:18, Bonita Montero wrote:

Am 09.08.2024 um 20:19 schrieb David Brown:

On 09/08/2024 20:08, Bonita Montero wrote:

Am 08.08.2024 um 19:47 schrieb David Brown:
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Think about negating a value.  For two's complement, that means inverting each bit and then adding 1.  For sign-magnitude, you
invert  the sign bit. For ones' complement, you invert each bit.

>
But with one's complement you have the same circuits for ading
and substracting like with unsigned values.

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If you are trying to say that for two's complement, "a + b" and "a - b" use the same circuits regardless of whether you are doing signed or unsigned arithmetic, then that is correct.  It is one of the reasons why two's complement became the dominant format.
>

 ... and you've got one more value since there's no negative and
positive zero.
 

It's rarely significant that there's an extra value for signed integers - it's just one more out of 4 billion for 32-bit ints.  (It's vital that you have all possible patterns for unsigned data.)
It is, I would say, nice that you don't have two different zero representations.
But sometimes it would be nice if INT_MIN were equal to -INT_MAX, and that there was an extra pattern available for an invalid or special value.  It could provide a very compact representation for a type that is either a valid integer or a "No result" indicator, much like a NaN for floating point.  Of course, it's possible to use two's complement and reserve 0x8000'0000 (or whatever number of zeros are needed) for the purpose.