Not currently (though we have "Unknown"). The main problem is the
interaction with Python booleans and the operators "or", "and", "not"
(which are *not* logical operators). The Sage "Unknown" is badly
broken for these reasons
sage: not Unknown # waiting for Unknown
True
sage: Unknown or False # waiting for Unknown
False
So be careful if you start using it!
If we would use the correct logical operators ~ (for negation), ^ (for
xor) and & (for and) then we might be able to come up with something.
But Sage sort of ignore them.
This problem has been discussed a lot on this mailing list and there
even exists a (refused) PEP request in this direction.
Best,
Vincent
On 15 November 2016 at 08:22, Thierry Dumont <tdum...@math.univ-lyon1.fr> wrote:
> When developing a software which aims to prove something, it seems
> necessary to be able to return something in
> {True, False, Indeterminate}.
>
> Of course, there are many possibilities to do this, but is there a
> "canonical" one in Sage ?
>
> In C++, for example, there exists the Boost Tribool library
> (http://www.boost.org/doc/libs/1_62_0/doc/html/tribool.html#tribool.introduction)
> .
>
> t.d.
>
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