#=> and #<=> constraints

  Hi there,

    I've been trying to use the #=> and #<=> constraints in Eclipse but 
keep getting a syntax error which I don't understand. The code I've 
written is to use channeling constraints to enforce a permutation on a 
set of variables:

channelling(N,X) :-
    % Primal Model
    dim(X, [N]),
    X[1..N] :: 1..N,

    % Dual Model
    dim(R, [N]),
    R[1..N] :: 1..N,

    (for(I,1,N), param(N,X,R) do
        (for (J,1,N), param(I,X,R) do
            X[I] #= J #=> R[J] #= I,
            R[J] #= I #=> X[I] #= J
            )
        ),
    X =.. [_|Vars],
    writeln("Setup complete..."),
    labeling(Vars).

I keep getting an error from Eclipse:

| file testing.ecl, line 17: syntax error: postfix/infix operator expected
|         X[I] #= J #=> R[J] #= I,
|                       ^ here

Also, I would have expected to be able to be able to write the above 
code using the #<=> constraint as follows:

channelling(N,X) :-
    % Primal Model
    dim(X, [N]),
    X[1..N] :: 1..N,

    % Dual Model
    dim(R, [N]),
    R[1..N] :: 1..N,

    (for(I,1,N), param(N,X,R) do
        (for (J,1,N), param(I,X,R) do
            X[I] #= J #<=> R[J] #= I,
            )
        ),
    X =.. [_|Vars],
    writeln("Setup complete..."),
    labeling(Vars).

When I tried the following code using "=>" instead:

channelling(N,X) :-
    % Primal Model
    dim(X, [N]),
    X[1..N] :: 1..N,

    % Dual Model
    dim(R, [N]),
    R[1..N] :: 1..N,

    (for(I,1,N), param(N,X,R) do
        (for (J,1,N), param(I,X,R) do
            X[I] #= J => R[J] #= I,
            R[J] #= I => X[I] #= J
            )
        ),
    X =.. [_|Vars],
    writeln("Setup complete..."),
    labeling(Vars).


I got the desired result but I don't think that semantically this 
correct since it is the logical implies
rather than the constraint implication.

I also tried:

channelling(N,X) :-
    % Primal Model
    dim(X, [N]),
    X[1..N] :: 1..N,

    % Dual Model
    dim(R, [N]),
    R[1..N] :: 1..N,

    (for(I,1,N), param(N,X,R) do
        (for (J,1,N), param(I,X,R) do
            X[I] = J #=> R[J] = I,
            R[J] = I #=> X[I] = J
            )
        ),
    X =.. [_|Vars],
    writeln("Setup complete..."),
    labeling(Vars).

...but I get the same syntax error as above.

If anyone could shed some light on this for me I would be grateful.

Thanks,
Mark.