Mercurial > repos > other > SevenLanguagesInSevenWeeks
view 3-Prolog/day1-self-study.pl @ 57:c9873b78e8c2
Extra little thought on collaboration rule
author | IBBoard <dev@ibboard.co.uk> |
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date | Tue, 26 Sep 2017 20:47:20 +0100 |
parents | 2bbb377ddeb0 |
children | 49cb2f7af872 |
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% Make a KB of books and authors and query it. book(the_long_earth). book(night_watch). book(science_of_discworld). book(lord_of_the_rings). book(route_666). book(krokodil_tears). author(terry_pratchett). author(stephen_baxter). author(jack_cohen). author(ian_stewart). author(jrr_tolkein). author(jack_yeovil). wrote(terry_pratchett, the_long_earth). wrote(stephen_baxter, the_long_earth). wrote(terry_pratchett, night_watch). wrote(terry_pratchett, science_of_discworld). wrote(jack_cohen, science_of_discworld). wrote(ian_stewart, science_of_discworld). wrote(jrr_tolkein, lord_of_the_rings). wrote(jack_yeovil, route_666). wrote(jack_yeovil, krokodil_tears). collaborated(Author1, Author2, Book) :- \+(Author1 = Author2), author(Author1), author(Author2), wrote(Author1, Book), wrote(Author2, Book), book(Book). collaborated(Author1, Author2) :- collaborated(Author1, Author2, Book). % collaborated(terry_pratchett, stephen_baxter). returns true, but collaborated(Author1, Author2). just says "no", as does % collaborated(terry_pratchett, OtherAuthor). - for some reason it isn't filling in answers. It does, however, correctly % say that Pratchett never collaborated with Pratchett. % % If I remove "\+(Author1 = Author2)" then it successfully returns stephen_baxter for terry_pratchett but also returns % Pratchett himself as a valid answer as well. % % wrote(terry_pratchett, Book). works to return all books by an author, though. % % However, having added a three-argument version, it can correctly identify the books that someone collaborated on if % you supply both authors but it won't supply an author when given one author and the book title.