Tests/leq.chr

   1 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   2 %%
   3 %% simple constraint solver for inequalities between variables
   4 %% thom fruehwirth ECRC 950519, LMU 980207, 980311
   5 %%
   6 %% ported to hProlog by Tom Schrijvers
   7
   8 :- module(leq,[leq/0]).
   9 :- use_module(library(chr)).
  10
  11 :- constraints leq/2.
  12
  13 reflexivity  @ leq(X,X) <=> true.
  14 antisymmetry @ leq(X,Y), leq(Y,X) <=> X = Y.
  15 idempotence  @ leq(X,Y) \ leq(X,Y) <=> true.
  16 transitivity @ leq(X,Y), leq(Y,Z) ==> leq(X,Z).
  17
  18 leq :-
  19         circle(X, Y, Z),
  20         \+ attvar(X),
  21         X == Y,
  22         Y == Z.
  23
  24 circle(X, Y, Z) :-
  25         leq(X, Y),
  26         leq(Y, Z),
  27         leq(Z, X).