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Prolog Source  |  1990-03-26  |  582 b   |  25 lines
  1. /*
  2.    Copyright (c) 1986, 90 by Prolog Development Center
  3. */
  4.    
  5. domains
  6.    town     = symbol
  7.    distance = integer
  8.  
  9. predicates
  10.    road(town, town, distance)
  11.    route(town, town, distance)
  12.  
  13. clauses
  14.    road(tampa, houston, 200).
  15.    road(gordon, tampa, 300).
  16.    road(houston, gordon, 100).
  17.    road(houston, kansas_city, 120).
  18.    road(gordon, kansas_city, 130).
  19.    route(Town1, Town2, Distance) :-
  20.       road(Town1, Town2, Distance).
  21.    route(Town1, Town2, Distance) :-
  22.       road(Town1, X, Dist1),
  23.       route(X, Town2, Dist2),
  24.       Distance=Dist1+Dist2, !.
  25.