167 lines
3.8 KiB
Prolog
167 lines
3.8 KiB
Prolog
%% Follows 'Coding guidelines for Prolog' - Theory and Practice of Logic Programming
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%% https://doi.org/10.1017/S1471068411000391
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polynomial_variables([x, y, z]).
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polynomial_variable_p(X) :-
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polynomial_variables(V), member(X, V).
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power_p(X) :-
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polynomial_variable_p(X), !.
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power_p(X^N) :-
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polynomial_variable_p(X), integer(N), N > 1, !.
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%% coefficient_p(K) :-
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%% number(K).
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%% term_p(X) :-
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%% polynomial_variable_p(X), !.
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term_p(N) :-
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number(N).
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term_p(X) :-
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power_p(X).
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term_p(L * R) :-
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term_p(L),
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term_p(R), !.
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polynomial_p(M) :-
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term_p(M).
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polynomial_p(L + R) :- % Left greedy
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polynomial_p(L), !, % Why?
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term_p(R), !.
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%% ?- polynomial_p(3*x^2+y*z).
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%@ true.
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%% ?- polynomial_p(x^100*y*z).
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%@ true.
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%% ?- polynomial_p(x+y+z).
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%@ true.
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%@ false.
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%@ false.
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%% ?- polynomial_p(3*x^2+y*z+x^100*y*z).
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%@ true.
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%@ true .
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%@ false.
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%@ false.
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%@ false.
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%@ false.
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simplify_term(1 * P, P) :-
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term_p(P), !.
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simplify_term(0 * _, 0) :-
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!.
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simplify_term(T, S) :-
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term_to_list(T, L),
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sort(L, L2),
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join_like_terms(L2, S).
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%% ?- simplify_term(2*y*z*x^3*x, X).
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%@ X = [2, x^1, x^3, y^1, z^1].
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join_like_terms([T1, T2 | L], [P^N | L]) :-
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P^N1 is T,
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P^N2 is T2,
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N is N1 + N2,
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!.
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join_like_terms([N1, N2 | L], [N | L]) :-
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N is N1 * N2,
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!.
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join_like_terms(T, T).
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%% ?- join_like_terms([2, 3, x^1, x^2], T).
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%@ ERROR: Arguments are not sufficiently instantiated
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%@ ERROR: In:
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%@ ERROR: [9] _3138^_3140 is _3134
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%@ ERROR: [8] join_like_terms([2,3|...],[_3188^_3190,...|...]) at /tmp/ediprologODLYxF:62
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%@ ERROR: [7] <user>
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%@ Exception: (8) join_like_terms([2, 3, x^1, x^2], _2428) ? abort
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%@ % Execution Aborted
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%@ T = [6, x^1, x^2].
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%@ T = [6, x^1].
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%@ T = [6].
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%@ T = [2].
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term_to_list(L * N, [N | TS]) :-
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number(N),
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term_to_list(L, TS), !.
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term_to_list(L * T, [T2 | TS]) :-
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power_p(T),
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power_to_canon(T, T2),
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term_to_list(L, TS), !.
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term_to_list(T, [T]).
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power_to_canon(T, T^1) :-
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polynomial_variable_p(T).
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power_to_canon(T^N, T^N) :-
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polynomial_variable_p(T).
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simplify_polynomial(M, M2) :-
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term_p(M), simplify_term(M, M2), !.
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simplify_polynomial(P + 0, P) :-
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term_p(P), !.
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simplify_polynomial(0 + P, P) :-
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term_p(P), !.
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simplify_polynomial(P + M, P2 + M2) :-
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simplify_polynomial(P, P2), simplify_term(M, M2).
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simplify_polynomial(P + M, P2 + M3) :-
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monomial_parts(M, _, XExp),
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delete_monomial(P, XExp, M2, P2), !,
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add_monomial(M, M2, M3).
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simplify_polynomial(P + M, P2 + M2) :-
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simplify_polynomial(P, P2), simplify_term(M, M2).
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%% ?- simplify_polynomial(1*x+(-1)*x, P).
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monomial_parts(X, 1, X) :-
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power_p(X), !.
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monomial_parts(X^N, 1, X^N) :-
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power_p(X^N), !.
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monomial_parts(K * M, K, M) :-
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coeficient_p(K), !.
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monomial_parts(K, K, indep) :-
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coeficient_p(K), !.
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delete_monomial(M, X, M, 0) :-
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term_p(M),
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monomial_parts(M, _, X), !.
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delete_monomial(M + M2, X, M, M2) :-
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term_p(M2), term_p(M),
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monomial_parts(M, _, X), !.
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delete_monomial(P + M, X, M, P) :-
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term_p(M), monomial_parts(M, _, X), !.
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delete_monomial(P + M2, X, M, P2 + M2) :-
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delete_monomial(P, X, M, P2).
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add_monomial(K1, K2, K3) :-
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number(K1), number(K2), !,
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K3 is K1 + K2.
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add_monomial(M1, M2, M3) :-
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monomial_parts(M1, K1, XExp),
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monomial_parts(M2, K2, XExp),
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K3 is K1 + K2,
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p_aux_add_monomial(K3, XExp, M3).
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p_aux_add_monomial(K, indep, K) :-
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!.
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p_aux_add_monomial(0, _, 0) :-
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!.
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p_aux_add_monomial(1, XExp, XExp) :-
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!.
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p_aux_add_monomial(K, XExp, K * XExp).
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closure_simplify_polynomial(P, P) :-
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simplify_polynomial(P, P2),
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P==P2, !.
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closure_simplify_polynomial(P, P3) :-
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simplify_polynomial(P, P2),
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closure_simplify_polynomial(P2, P3), !.
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%% ?- simplify_polynomial(1*x+(-1)*x, P).
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%@ P = x+ -1*x .
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%@ P = x+ -1*x
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%@ Unknown action: q (h for help)
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%@ Action?
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%@ Unknown action: q (h for help)
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%@ Action? .
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