Tristate - wanna?

[Andrei Alexandrescu]

On 10/26/13 12:17 PM, Walter Bright wrote:
> On 10/26/2013 8:42 AM, Andrei Alexandrescu wrote:
>> While messing with std.allocator I explored the type below. I ended up
>> not using
>> it, but was surprised that implementing it was quite nontrivial.
>> Should we add
>> it to stdlib?
>>
>> Theory: http://en.wikipedia.org/wiki/Three-state_logic
>
> When I worked on the ABEL programming language, which was for designing
> programmable logic devices, we found it useful to have an additional
> state, "don't care".

Yah, that would be four-valued logic: 
http://en.wikipedia.org/wiki/Four-valued_logic.

One challenge in Tristate (or the as-of-yet-unwritten Fourstate) is to 
define the primitives |, &, ^, and ~ with minimum of operations. For 
example Tristate still has conditionals in two of them, which I think 
could be cleverly avoided.


Andrei