28 lines
691 B
Prolog
28 lines
691 B
Prolog
:- module(arithmetic, [msb/2, lsb/2]).
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:- use_module(library(error)).
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lsb(X, N) :-
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builtins:must_be_number(X, lsb/2),
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( \+ integer(X) -> type_error(integer, X, lsb/2)
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; X < 1 -> domain_error(not_less_than_one, X, lsb/2)
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; builtins:can_be_number(N, lsb/2),
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X1 is X /\ (-X),
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msb_(X1, -1, N)
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).
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msb(X, N) :-
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builtins:must_be_number(X, msb/2),
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( \+ integer(X) -> type_error(integer, X, msb/2)
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; X < 1 -> domain_error(not_less_than_one, X, msb/2)
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; builtins:can_be_number(N, msb/2),
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X1 is X >> 1,
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msb_(X1, 0, N)
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).
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msb_(0, N, N) :- !.
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msb_(X, M, N) :-
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X1 is X >> 1,
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M1 is M + 1,
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msb_(X1, M1, N).
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