if statement - prolog query ignores if conditional -



if statement - prolog query ignores if conditional -

first , foremost 'noob' regards prolog, , finding hard find info online appropriate skill level. anyway here sample of code:

book(brave_new_world). book(lord_of_the_flies). book(fight_club). book(wind_in_the_willows). book(the_hobbit). cat_num(111) :- book(brave_new_world). cat_num(222) :-book(lord_of_the_flies). cat_num(333) :- book(fight_club). cat_num(444) :- book(wind_in_the_willows). cat_num(555) :-book(the_hobbit). author(huxley_aldus) :- book(brave_new_world). author(golding_william) :- book(lord_of_the_flies). author(palahniuk) :- book(fight_club). author(palahniuk_chuck) :- book(fight_club). author(tolkien_jrr) :- book(the_hobbit). author_sur(palahniuk) :- book(fight_club). author_sur(golding) :- book(lord_of_the_flies). author_sur(huxley) :- book(brave_new_world). author_sur(grahame) :-book(wind_in_the_willows). author_sur(tolkien) :-book(the_hobbit). author_fore(aldus) :- book(brave_new_world). author_fore(william) :- book(lord_of_the_flies). author_fore(chuck) :- book(fight_club). author_fore(kenneth) :- book(wind_in_the_willows). author_fore(jrr) :-book(the_hobbit).

however when querying kb ?- cat_num(222), book(x). not homecoming result want (lord_of_the_flies). guidance in i'm going wrong appreciated.

after doing changes suggested, have reached hurdle: how set rule determine whether book borrowed or overdue? (code follows)

number_book(111, brave_new_world). number_book(222, lord_of_the_flies). number_book(333, fight_club). number_book(444, wind_in_the_willows). number_book(555, the_hobbit). author_book(huxley_aldus, brave_new_world). author_book(golding_william, lord_of_the_flies). author_book(palahniuk_chuck, fight_club). author_book(grahame_kenneth, wind_in_the_willows). author_book(tolkien_jrr, the_hobbit). author_fore_sur(huxley_aldus, aldus, huxley). author_fore_sur(golding_william, william, golding). author_fore_sur(palahniuk_chuck, chuck, palahniuk). author_fore_sur(grahame_kenneth, kenneth, grahame). author_fore_sur(tolkien_jrr, jrr, tolkien). id_sur_fore(1202, smith, john). id_sur_fore(1332, thompson, kevin). id_sur_fore(4556, anderson, edward). house_post_id(5, dh1_3pr, 1202). house_post_id(123, ne3_4ty, 1332). house_post_id(45, dh3_6kl, 4556). borrowed_id(333, 1202). borrowed_id(222, 1332). borrowed_id(555, 4556). loan_due_id(11_06_2014, 27_06_2014, 333). loan_due_id(15_06_2014, 01_07_2014, 222). loan_due_id(17_06_2014, 13_07_2014, 555).

in program, have predicates single argument. not create much sense since want found relations between things. catalog number , book title. instead, want:

number_book(111, brave_new_workd). number_book(222, lord_of_the_flies). ... author_book(golding_william, lord_of_the_flies). ... author_fore_sur(golding_william, william,golding).

alternatively might want 1 single table:

number_book_author(222, lord_of_the_flies, golding_william).

now can ask:

?- number_book(222, x). x = lord_of_the_flies.

rules come play later, say

number_book_author(nr, b, a) :- number_book(nr, b), author_book(a, b).

if-statement prolog conditional

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