declare
proc {Impl X Y} {FD.impl X Y 1} end %% only simple implications
`~`=FD.nega % ~ is syntax for negation
proc {Kibi Sol}
K % Kibi's sex: 0 male, 1 female
P1 % sex of 1st parent
P2 % sex of 2nd parent
KC % Kibi's claim: 0 for "I am a boy", 1 for "I am a girl"
TK % truth of Kibi's claim
T1 % truth of 1st statement
T2 % truth of 2nd statement
T3 ] % truth of 3rd statement
NP2=~P2
in
Sol = [K P1 P2 KC TK T1 T2 T3]
Sol ::: 0#1
{Impl ~K TK} % if Kibi is male then his statement is true
{FD.equi KC K} = TK % Kibi tells the truth iff his claim tells his sex
T1 = ~KC % the 1st statement describes Kibi's claim
K = T2 % the 2nd statement describes Kibi's sex
T3 = ~TK % the 3rd statement describes the truth of Kibi's claim
P1 = NP2 % P1 and P2 have opposite sexes
{Impl ~P1 T1} % if P1 is male then T1
{Impl NP2 T2} % if P2 is male then T2
{Impl NP2 T3} % if P2 is male then T3
{Impl P2 {FD.exor T2 T3}} % if P2 is female then either T2 or T3
{FD.distribute naive Sol}
end
{ExploreAll Kibi}
Output:
(1|1|0|0|0|1|1|1|nil)|nil
Thus Kibi is a girl, the first parent is her mother and the second her father,
and she claimed to be a boy. The search tree has only two choice points and two failure nodes.