Error in PROLOG program -

Error in PROLOG program -

in code below, i'm getting error in sister function "illegal character" in **

blockquote

person \= p1** (\= not equal to)

blockquote

domains person = symbol

predicates parent(person,person) female(person) male(person) mother(person,person) father(person,person) grandfather(person,person) grandmother(person,person) sister(person,person)

clauses female(merry). female(syndra). female(juliet). female(lisa).

male(parker). male(peter). male(herry). male(bob). male(paul). parent(juliet,lisa). parent(bob,lisa). parent(bob,paul). parent(bob,merry). parent(juliet,paul). parent(juliet,merry). parent(peter,herry). parent(lisa,herry). parent(merry,parker). parent(merry,syndra). father(x,person):-parent(x,person) , male(x). mother(x,person):-parent(x,person) , female(x). grandfather(x,person):-parent(y,person),father(x,y). grandmother(x,person):-parent(y,person),mother(x,y). sister(x,person):-parent(z,x),parent(z,person),person \= p1,female(person).

not sure about, , can't seek because don't have turbo prolog right now, vaguely remember variables doesn't need declared.

and suspect kid should person instead (after all, kid is person). seek simplify in way

domains person = symbol predicates parent(person,person) female(person) male(person) mother(person,person) ...

prolog turbo-prolog