https://www.boost.org/library/1.79.0/logictribool/
Boost.Tribool (1.79.0)
3-state boolean type library.
boosttribool1790
https://www.boost.org/doc/libs/1_38_0/doc/html/boost/logic/tribool.html
Class tribool
classtribool
https://www.boost.org/doc/libs/1_59_0/doc/html/tribool.html
Chapter 32. Boost.Tribool
chapter 32boosttribool
https://www.boost.org/doc/libs/1_53_0/doc/html/boost/logic/tribool.html
Class tribool
classtribool
https://www.boost.org/library/1.68.0/logictribool/
Boost.Tribool (1.68.0)
3-state boolean type library.
1 68boosttribool0
https://www.boost.org/doc/libs/1_68_0/doc/html/tribool.html
Chapter 22. Boost.Tribool
chapter 22boosttribool
https://www.boost.org/doc/libs/1_38_0/doc/html/BOOST_TRIBOOL_THIRD_STATE.html
Macro BOOST_TRIBOOL_THIRD_STATE
macroboosttriboolthirdstate
https://www.boost.org/library/1.76.0/logictribool/
Boost.Tribool (1.76.0)
3-state boolean type library.
boosttribool1760