kind_von(karl_VI, leopold_I).
kind_von(maria_theresia, karl_VI).
kind_von(joseph_II, maria_theresia).
kind_von(joseph_II, franz_I).
kind_von(leopold_II, maria_theresia).
kind_von(marie_antoinette, maria_theresia).
:- kind_von(Kind, Elternteil).
:- kind_von(joseph_II, friedrich_II).
! Zusicherung gescheitert
-----         n599 ------------------------
Goals that do not succeed are reported as errors. In this case the predicate is correct (Joseph's II father is Franz I and not Friedrich II) - and the goal should not succeed. With :/- instead of :- we state that a goal should fail. The non standard operator :/- is used to prevent premature usage of negation.
**NEXT:Change :- to :/- and press [DO].
[logprog|GUPU|UWN]