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Add predicate lcm/2 to library(arithmetic)

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This commit is contained in:
Adrián Arroyo Calle
2022-12-11 21:49:41 +01:00
parent d660e4244f
commit 5f2c77fa74
1 changed files with 17 additions and 1 deletions
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18
src/lib/arithmetic.pl
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@@ -1,4 +1,4 @@
:- module(arithmetic, [expmod/4, lsb/2, msb/2, number_to_rational/2, :- module(arithmetic, [expmod/4, lcm/3, lsb/2, msb/2, number_to_rational/2,
number_to_rational/3, popcount/2, number_to_rational/3, popcount/2,
rational_numerator_denominator/3]). rational_numerator_denominator/3]).
@@ -28,6 +28,22 @@ expmod_(Base0, Expo0, Mod, C, R) :-
Base is (Base0 * Base0) mod Mod, Base is (Base0 * Base0) mod Mod,
expmod_(Base, Expo, Mod, C, R). expmod_(Base, Expo, Mod, C, R).
%% lcm(+A, +B, -Lcm) is det.
%
% Calculates the Least common multiple for A and B: the smallest positive integer
% that is divisible by both A and B.
%
% A and B need to be integers.
lcm(A, B, X) :-
builtins:must_be_number(A, lcm/2),
builtins:must_be_number(B, lcm/2),
( \+ integer(A) -> type_error(integer, A, lcm/2)
; \+ integer(B) -> type_error(integer, B, lcm/2)
; (A = 0, B = 0) -> X = 0
; builtins:can_be_number(X, lcm/2),
X is abs(B) // gcd(A,B) * abs(A)
).
lsb(X, N) :- lsb(X, N) :-
builtins:must_be_number(X, lsb/2), builtins:must_be_number(X, lsb/2),
( \+ integer(X) -> type_error(integer, X, lsb/2) ( \+ integer(X) -> type_error(integer, X, lsb/2)