Example Money

Jan Burse, created Sep 15. 2018
```/**
* Prolog code for the backtracking example.
*
* Puzzle originally published July 1924 issue of
* Strand Magazine by Henry Dudeney
*
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% oneof(+List,-Elem,-List)
oneof([X|Y], X, Y).
oneof([X|Y], Z, [X|T]) :-
oneof(Y, Z, T).

% assign(-List,+List)
assign([], _).
assign([X|Y], L) :-
oneof(L, X, R),
assign(Y, R).

% puzzle(-List)
puzzle(X) :-
X = [S,E,N,D,M,O,R,Y],
assign(X, [0,1,2,3,4,5,6,7,8,9]),
M =\= 0,
S =\= 0,
1000*S+100*E+10*N+D+1000*M+100*O+10*R+E =:= 10000*M+1000*O+100*N+10*E+Y.
```