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Merge pull request #391 from notoria/msb_lsb2

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Implemented lsb/2 and msb/2
This commit is contained in:
Mark Thom
2020-04-25 12:58:03 -03:00
committed by GitHub
parent e27c2b59c8 1873b655a8
commit a2400767ed
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).