Task
Given two sets A and B, compute 



(
A
∖
B
)
∪
(
B
∖
A
)
.


{\displaystyle (A\setminus B)\cup (B\setminus A).}



That is, enumerate the items that are in A or B but not both. This set is called the symmetric difference of A and B.

In other words: 



(
A
∪
B
)
∖
(
A
∩
B
)


{\displaystyle (A\cup B)\setminus (A\cap B)}

 (the set of items that are in at least one of A or B minus the set of items that are in both A and B).

Optionally, give the individual differences (



A
∖
B


{\displaystyle A\setminus B}

 and 



B
∖
A


{\displaystyle B\setminus A}

) as well.



Test cases
A = {John, Bob, Mary, Serena}
B = {Jim, Mary, John, Bob}



Notes
 If your code uses lists of items to represent sets then ensure duplicate items in lists are correctly handled. For example two lists representing sets of a = ["John", "Serena", "Bob", "Mary", "Serena"] and b = ["Jim", "Mary", "John", "Jim", "Bob"] should produce the result of just two strings: ["Serena", "Jim"], in any order.
 In the mathematical notation above A \ B gives the set of items in A that are not in B; A ∪ B gives the set of items in both A and B, (their union); and A ∩ B gives the set of items that are in both A and B (their intersection).


sym_diff :-
    A = ['John', 'Serena', 'Bob', 'Mary', 'Serena'],
    B = ['Jim', 'Mary', 'John', 'Jim', 'Bob'],
    format('A : ~w~n', [A]),
    format('B : ~w~n', [B]),
    list_to_set(A, SA),
    list_to_set(B, SB),
    format('set from A : ~w~n', [SA]),
    format('set from B : ~w~n', [SB]),
    subtract(SA, SB, DAB),
    format('difference A\\B : ~w~n', [DAB]),
    subtract(SB, SA, DBA),
    format('difference B\\A : ~w~n', [DBA]),
    union(DAB, DBA, Diff),
    format('symetric difference : ~w~n', [Diff]).