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Prolog Source  |  1986-10-07  |  504 b   |  22 lines
  1. /* Program 13 */
  2. /*
  3.   Goal to enter is on page 51 of the manual.
  4.   Other goals to try are on pages 52-53.
  5. */
  6.  
  7. domains
  8.     title,author = symbol
  9.     pages        = integer
  10.     publication  = book(title,pages)
  11.  
  12. predicates
  13.     written_by(author,publication)
  14.     long_novel(publication)
  15.  
  16. clauses
  17.     written_by(fleming,book("DR NO",210)).
  18.     written_by(melville,book("MOBY DICK",600)).
  19.     long_novel(book(Title,Length)):-
  20.         written_by(_,book(Title,Length)),
  21.         Length>300.
  22.