Usability issue: boost::tribool::value_t is public

[fekir]

The tribool interface is not very user-friendly, I saw more than once following error:

assignment:

boost::tribool v1 = boost::tribool::false_value;
boost::tribool v2 = boost::tribool::true_value;
boost::tribool v3 = boost::tribool::indeterminate_value;

comparison:

v1 == boost::tribool::false_value;
v2 == boost::tribool::true_value;
v3 == boost::tribool::indeterminate_value;

The issue is frequent because of auto completion.
Since operator==, operator safe_bool and the function indeterminate it is possible to query the status of boost::tribool, I do not think there are good reasons for the value_t to be public.

If boost::tribool::value_t is changed to private, some function like indeterminate and operator! needs to be made friends, but otherwise there should be no other issues.

[pdimov]

I presume that the trailing _value is a typo?

[pdimov]

In

boost::tribool v3 = boost::tribool::indeterminate_value _value;

and

v3 == boost::tribool::indeterminate_value _value;

I mean.

[fekir]

Yes, sorry, should have been

boost::tribool v3 = boost::tribool::indeterminate_value;
v3 == boost::tribool::indeterminate_value;

I've updated the first description, thanks!