:- use_module(library(clpfd)).

% 6.1
schedule(C1, C2, C3, C4, C5) :-
    % domains
    member(C1, [a]),
    member(C2, [a,c]),
    member(C3, [a,b,c]),
    member(C4, [a,b,c]),
    member(C5, [a,c]),
    % constraints
    dif(C1, C2),
    dif(C1, C3),
    dif(C1, C5),
    dif(C3, C4),
    dif(C3, C5),
    dif(C4, C5).

% 6.3
bool(0).
bool(1).

show(0, false).
show(1, true).

csp(A1, B, C, D) :-
    bool(A),
    between(0, 3, B),
    between(0, 3, C),
    between(0, 6, D),
    A #==> B #=< 2,
    C #< 2 #==> A,
    B + C #< 4,
    B #> D,
    D #= 2 * C,
    show(A, A1).