rishi/scryer-prolog
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Enhanced number_to_rational/2 and number_to_rational/3

Browse Source
This commit is contained in:
notoria
2020-05-02 02:36:23 +02:00
parent 59b4c6dacb
commit 9df2df0f9f
1 changed files with 28 additions and 35 deletions
Download Patch File Download Diff File Expand all files Collapse all files

63
src/prolog/lib/arithmetic.pl
View File

@@ -30,54 +30,47 @@ msb_(X, M, N) :-
M1 is M + 1,
msb_(X1, M1, N).
number_to_rational(Real0, Fraction) :-
( var(Real0) -> instantiation_error(number_to_rational/2)
; Real0 = R1/R2 ->
( member(R, [R1, R2]), \+ number(R) ->
type_error(number, R, number_to_rational/2)
; Real = R1/R2
)
; number(Real0),
Real = Real0/1
),
number_to_rational(1.0e-6/1, Real, Fraction).
number_to_rational(Real, Fraction) :-
( var(Real) -> instantiation_error(number_to_rational/2)
; integer(Real) -> Fraction is Real rdiv 1
; (rational(Real) ; float(Real)) ->
number_to_rational(1.0e-6, Real, Fraction)
; type_error(number, Real, number_to_rational/2)
).
% If 0 <= Eps0 <= 1e-16 then the search is for "infinite" precision.
number_to_rational(Eps0, Real0, Fraction) :-
( var(Eps0) -> instantiation_error(number_to_rational/3)
; Eps0 = E0/E1 ->
( member(E, [E0, E1]), \+ number(E) ->
type_error(number, E, number_to_rational/3)
; Eps = E0/E1
)
; number(Eps0),
Eps = Eps0/1
; \+ number(Eps0) -> type_error(number, Eps0, number_to_rational/3)
; Eps0 < 0 -> domain_error(not_less_than_zero, Eps0, number_to_rational/3)
; Eps_ is Eps0 rdiv 1,
rational_numerator_denominator(Eps_, EpsN, EpsD),
Eps = EpsN/EpsD
),
( var(Real0) -> instantiation_error(number_to_rational/3)
; Real0 = R1/R2 ->
( member(R, [R1, R2]), \+ number(R) ->
type_error(number, R, number_to_rational/3)
; Real = R1/R2
)
; number(Real0),
Real = Real0/1
; \+ number(Real0) -> type_error(number, Eps0, number_to_rational/3)
; Real_ is Real0 rdiv 1,
rational_numerator_denominator(Real_, RealN, RealD),
Real = RealN/RealD
),
E0/E1 = Eps,
P0/Q0 = Real,
S is sign(E0) * sign(E1),
( S < 0 -> domain_error(not_less_than_zero, Eps0, number_to_rational/3)
; P1 is abs(P0),
Q1 is abs(Q0),
Qn1n is P1 * E1 - Q1 * E0,
( P0 < 0 -> I1 is -1 + P0 // Q0
; I1 is P0 // Q0
),
P1 is P0 mod Q0,
Q1 = Q0,
( P1 =:= 0 -> Fraction is I1 + 0 rdiv 1
; Qn1n is max(P1 * E1 - Q1 * E0, 0),
Qn1d is Q1 * E1,
Qn1 = Qn1n/Qn1d,
Qp1n is P1 * E1 + Q1 * E0,
Qp1d = Qn1d,
Qp1 = Qp1n/Qp1d,
stern_brocot_(Qn1, Qp1, 0/1, 1/0, P2/Q2),
P3 is sign(P0) * sign(Q0) * P2,
Fraction is P3 rdiv Q2
).
Fraction is I1 + P2 rdiv Q2
),
!.
number(X) :-
( integer(X)
@@ -98,8 +91,8 @@ stern_brocot_(Qnn/Qnd, Qpn/Qpd, A/B, C/D, Fraction) :-
simplify_fraction(A0/B0, A/B) :-
G is gcd(A0, B0),
A is A0 div G,
B is B0 div G.
A is A0 // G,
B is B0 // G.
rational_numerator_denominator(R, N, D) :-
write_term_to_chars(R, [], Cs),