56 lines
1.5 KiB
Perl
56 lines
1.5 KiB
Perl
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% solving linear polynomial equations by variable elimination a la Gauss
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% thom fruehwirth 910610,911213,920124,930602,931223, 980311
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% 961107 christian holzbaur for SICStus CHR
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% complete for equalities, leaves equalities implicit, slow
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% may loop if variables of the equations are unified
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:- use_module(library(chr)).
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:- ensure_loaded('math-utilities'). % load auxiliary file
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handler gauss.
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option(check_guard_bindings, on). % for delete(X...) in rule eliminate
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operator(100,xfx,equals).
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constraints (equals)/2.
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% Poly equals Const, where Poly is list of monomials Variable*Coefficient
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eliminate(X) @
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[X*Coeff1|P1] equals C1 \ P equals C2 <=> delete(X*Coeff2,P,P2) |
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is_div(Coeff2,Coeff1,C),
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mult_const(eq0(C1,P1),C,eq0(C1C,P1C)),
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add_eq0(eq0(C2,P2),eq0(C1C,P1C),eq0(C3,P3)),
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P3 equals C3.
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constraints {}/1.
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% curly brackets as wrapper to avoid name clash with built-in =:=
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split @ { C, Cs } <=> { C }, { Cs }.
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normalize @ {A =:= B} <=>
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normalize(A,B,Poly,Const),
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Poly equals Const.
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/*
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% uses math_portray pretty print defined in math-utilities.pl
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?- {3 * X + 2 * Y - 4 * (3 + Z) =:= 2 * (X - 3) + (Y + Z) * 7 ,
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2 * (X + Y + Z) =:= 3 * (X - Y - Z) ,
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5 * (X + Y) - 7 * X - Z =:= (2 + 1 + X) * 6}.
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-(6*Z)=:=6,
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-(35*Y)=:= -23,
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X=:= -1.7142857142857144 ?
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?- {3 * X + 2 * Y - 4 * (3 + Z) =:= 2 * (X - 3) + (Y + Z) * 7 ,
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2 * (X + Y + Z) =:= 3 * (X - Y - Z)}.
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-(6*Z)=:=6,
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-(5*Y)+X=:= -5 ?
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*/
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/* end of file gauss.chr ------------------------------------------------*/
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