28 lines
909 B
Prolog
28 lines
909 B
Prolog
%! damm_algorithm(+Number) is semidet.
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% Succeeds if the number is valid according to the Damm algorithm.
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damm_algorithm(Number) :-
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Matrix = [
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[0, 3, 1, 7, 5, 9, 8, 6, 4, 2],
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[7, 0, 9, 2, 1, 5, 4, 8, 6, 3],
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[4, 2, 0, 6, 8, 7, 1, 3, 5, 9],
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[1, 7, 5, 0, 9, 8, 3, 4, 2, 6],
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[6, 1, 2, 3, 0, 4, 5, 9, 7, 8],
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[3, 6, 7, 4, 2, 0, 9, 5, 8, 1],
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[5, 8, 6, 9, 7, 2, 0, 1, 3, 4],
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[8, 9, 4, 5, 3, 6, 2, 0, 1, 7],
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[9, 4, 3, 8, 6, 1, 7, 2, 0, 5],
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[2, 5, 8, 1, 4, 3, 6, 7, 9, 0]
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],
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number_codes(Number, Codes),
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foldl(damm_algorithm(Matrix), Codes, 0, 0).
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damm_algorithm(Matrix, Code, N0, N) :-
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Digit is Code - 48,
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nth0(N0, Matrix, Row),
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nth0(Digit, Row, N).
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:- foreach(member(Number, [5724, 5727, 112946, 112949]), (
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( damm_algorithm(Number) -> write(Number is valid) ; write(Number is invalid) ),
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nl
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)).
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