/* after opening this file, resave it as promotes.pro */

/* person1 likes person2 */
/* john likes mary */
likes(john, mary).   
/* likes  is a predicate */
/* john and mary are constants */
/* upper case indicates variables */

/* facts are headless Horn clauses */
tall(troy).
short (sarah).
tall (alex).
short (sean).

/* command to load code stored on disk */
/* is  consult('filename.pro').  *.
/* filename can't be more than 8 characters long */

/* stupid rule  - doesn't do what we want */
loves (Male, Female) :- likes (Female,Male).

/* mother (mother,child) */

mother(sarah,jane).

/* father (father, child) */

/* parent (parent, child ) :-  mother (parent,child).  */
parent (Parent,Child) :- mother (Parent,Child).

parent(Parent, Child) :- father (Parent,Child).
mother (margie, paul).
mother(sandra, sam).
mother (dolly, joe).
father (jack, billy).
father(jack, sam).
father(paul, joe).

/* married (man, woman) :-  mother(woman,child) , father (man, child) */
married (M,W) :- mother (W,C), father (M,C).