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Implemented lsb/2 and msb/2

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notoria
2020-04-24 22:47:24 +02:00
parent 31c868818b
commit 1873b655a8
1 changed files with 25 additions and 0 deletions
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src/prolog/lib/arithmetic.pl Normal file
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:- module(arithmetic, [msb/2, lsb/2]).
lsb(X, N) :-
builtins:must_be_number(X, lsb/2),
( \+ integer(X) -> throw(error(type_error(integer, X), lsb/2))
; X < 1 -> throw(error(domain_error(not_less_than_one, X), lsb/2))
; builtins:can_be_number(N, lsb/2),
X1 is X /\ (-X),
msb_(X1, -1, N)
).
msb(X, N) :-
builtins:must_be_number(X, msb/2),
( \+ integer(X) -> throw(error(type_error(integer, X), msb/2))
; X < 1 -> throw(error(domain_error(not_less_than_one, X), msb/2))
; builtins:can_be_number(N, msb/2),
X1 is X >> 1,
msb_(X1, 0, N)
).
msb_(0, N, N) :- !.
msb_(X, M, N) :-
X1 is X >> 1,
M1 is M + 1,
msb_(X1, M1, N).