NaNs Just Don't Get No Respect

[Simen Kjaeraas]

On Sun, 19 Aug 2012 05:52:01 +0200, Walter Bright  
<newshound2 at digitalmars.com> wrote:

> On 8/18/2012 8:31 PM, Adam D. Ruppe wrote:
>> enum BOOL {
>>     TRUE,
>>     FALSE,
>>     FILE_NOT_FOUND
>> }
>
> I used to work with digital electronics. There, "boolean" logic actually  
> had 4 states:
>
>      True
>      False
>      Don't Know
>      Don't Care
>

Like someone on Reddit mentioned, VHDL has 9 boolean states:

'U': uninitialized. This signal hasn't been set yet.
'X': unknown. Impossible to determine this value/result.
'0': logic 0
'1': logic 1
'Z': High Impedance
'W': Weak signal, can't tell if it should be 0 or 1.
'L': Weak signal that should probably go to 0
'H': Weak signal that should probably go to 1
'-': Don't care.

-- 
Simen