Re: [Boost-users] tribool question

From: Paul Johnson (gt54-boost_at_[hidden])
Date: 2005-08-11 03:35:32

I've had delivery turned off for the last month, so this probably won't 
thread correctly...

This is similar to the issue of modelling logic in hardware description 
languages. Verilog, for example, has a 4-value type which is pretty much 
identical to tribool, except that it adds an additional 'tristate' 
value. Some objects default unknown, some tristate.

VHDL has a more comprehensive (user-defined) 9-value logic type, which 
defaults to uninitialised. Logic on this type is fairly complex, but it 
includes both the obvious uninit and unknown semantics, and objects 
default to uninitialised. Having something like this as a tribool 
extension would be *very* useful. At a minimum, a usable type should 
have 4 values (U,0,1,X for uninit,0,1,unknown) and should default to U.

Maybe I'll get around to this one day... :)

Paul