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yap-6.3/CHR/chr/examples/math-fourier.pl

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% Slim Abdennadher, Thom fruehwirth, LMU, July 1998
% Straightforward Fourier Solver for linear inequations
% may loop because of producing more and mor eredundant equations
% compare to gauss.pl and fougau.pl
:- use_module(library(chr)).
:- ['math-utilities.pl']. % load auxiliary file
:- use_module( library(lists), [member/2, memberchk/2,select/3]).
handler gauss.
option(check_guard_bindings, on). % for delete(X...)
option(already_in_store, off).
option(already_in_heads, off).
operator(100,xfx,leq).
constraints (leq)/2.
redundant @
[X*Coeff1|P1] leq C1 \ P leq C2 <=>
delete(X*Coeff2,P,P2),
is_div(Coeff2,Coeff1,C),
C < 0,
mult_const(eq0(C1,P1),C,eq0(C1C,P1C)),
add_eq0(eq0(C2,P2),eq0(C1C,P1C),eq0(C3,P3)),
P3=[], 0 >= C3
|
true.
propagate(X) @
[X*Coeff1|P1] leq C1, P leq C2 ==>
delete(X*Coeff2,P,P2),
is_div(Coeff2,Coeff1,C),
C > 0
|
mult_const(eq0(C1,P1),C,eq0(C1C,P1C)),
add_eq0(eq0(C2,P2),eq0(C1C,P1C),eq0(C3,P3)),
P3 leq C3.
zero @ [] leq C1 <=> 0 =< C1.
constraints {}/1.
% curly brackets as wrapper to avoid name clash with built-in =:= etc.
split @ { C, Cs } <=> { C }, { Cs }.
normalize @ {A >= B} <=> {B =< A}.
normalize @ {A =:= B} <=> {A >= B}, {B =< A}.
normalize @ {A =< B} <=>
normalize(A,B,Poly,Const),
Poly leq Const.
/*
3 * X + 2 * Y - 4 * (3 + Z) =:= 2 * (X - 3) + (Y + Z) * 7 ,
2 * (X + Y + Z) =:= 3 * (X - Y - Z) ,
5 * (X + Y) - 7 * X - Z =:= (2 + 1 + X) * 6.
*/