%   File   : magic3.pl
%   Author : Neng-Fa ZHOU
%   Date   : 1992
%   Purpose: solve the magic square puzzle for a 3*3 board

top:-
    vars_constraints(Vars),
    labeling(Vars).
%    write(Vars).

mylabeling([]).
mylabeling([V|Vs]):-
    indomain(V),
    mylabeling(Vs).

go:-
    statistics(runtime,[Start|_]),
    top,
    statistics(runtime,[End|_]),
    T is End-Start,
    write('execution time is '),write(T), write(milliseconds),nl.


vars_constraints(Vars):-
    Vars=[X1,X2,X3,X4,X5,X6,X7,X8,X9],
    Vars in 1..9,
    alldifferent(Vars),
    X1+X2+X3#=15,
    X4+X5+X6#=15,
    X7+X8+X9#=15,
    X1+X4+X7#=15,
    X2+X5+X8#=15,
    X3+X6+X9#=15,
    X1+X5+X9#=15,
    X3+X5+X7#=15.