From 7d78a123ef820a7a0ed9f29df7cebbbc247134eb Mon Sep 17 00:00:00 2001
From: Diogo Cordeiro <diogo@fc.up.pt>
Date: Tue, 20 Nov 2018 01:48:23 +0000
Subject: [PATCH] Added polynomial_to_list, list_to_polynomial and
 scale_polynomial

---
 polimani.pl | 82 ++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 72 insertions(+), 10 deletions(-)

diff --git a/polimani.pl b/polimani.pl
index 75504ff..1d540e4 100644
--- a/polimani.pl
+++ b/polimani.pl
@@ -1,3 +1,4 @@
+%% vim: set softtabstop=4 shiftwidth=4 tabstop=4 expandtab:
 %% -*- mode: prolog-*-
 %% Follows 'Coding guidelines for Prolog' - Theory and Practice of Logic Programming
 %% https://doi.org/10.1017/S1471068411000391
@@ -19,7 +20,7 @@ polynomial_variable(X) :-
 polynomial_variable(P) :-
     polynomial_variable_list(V),
     member(X, V),
-    P = X^N.
+    P = X^_.
 %% Tests:
 %% ?- term_to_list(X, [x^4]).
 %@ X = x^4 .
@@ -61,15 +62,15 @@ term(L * R) :-
 %  predicate the problem ocurred.
 %
 is_term_valid_in_predicate(T, F) :-
-(
+    (
         term(T)
-;
+    ;
         write("Invalid term in "),
         write(F),
         write(": "),
         write(T),
         fail
-).
+    ).
 %% Tests:
 %% ?- is_term_valid_in_predicate().
 
@@ -139,8 +140,8 @@ simplify_term(T, T2) :-
     sort(0, @=<, L, L2),
     join_like_terms(L2, L3),
     list_to_term(L3, T2). 	% Responsible for parenthesis
-    %% sort(0, @>=, L3, L4),
-    %% term_to_list(T2, L4).
+%% sort(0, @>=, L3, L4),
+%% term_to_list(T2, L4).
 %% Tests:
 %% ?- simplify_term(2*y*z*x^3*x, X).
 %@ X = 2*(x^4*(y*z)).
@@ -182,20 +183,24 @@ join_like_terms([], []).
 %% simplify_polynomial(+P:atom, -P2:atom) is det
 %
 %  Simplifies a polynomial.
+%  TODO: not everything is a +, there are -
 %
 simplify_polynomial(M, M2) :-
     %% Are we dealing with a valid term?
-    is_term_valid_in_predicate(M, "simplify_polynomial(M, M2)"),
+    %is_term_valid_in_predicate(M, "simplify_polynomial(M, M2)"),
+    term(M),
     %% If so, simplify it.
     simplify_term(M, M2),
     !.
 simplify_polynomial(P + 0, P) :-
     %% Ensure valid term
-    is_term_valid_in_predicate(P, "simplify_polynomial(P + 0, P)"),
+    %is_term_valid_in_predicate(P, "simplify_polynomial(P + 0, P)"),
+    term(P),
     !.
 simplify_polynomial(0 + P, P) :-
     %% Ensure valid term
-    is_term_valid_in_predicate(P, "simplify_polynomial(0 + P, P)"),
+    %is_term_valid_in_predicate(P, "simplify_polynomial(0 + P, P)"),
+    term(P),
     !.
 simplify_polynomial(P + M, P2 + M2) :-
     simplify_polynomial(P, P2),
@@ -215,7 +220,6 @@ simplify_polynomial(P + M, P2 + M2) :-
 %
 %  Simplifies a list of polynomials
 %
-
 simplify_polynomial_list([L1], L3) :-
     simplify_polynomial(L1, L2),
     L3 = [L2].
@@ -226,6 +230,64 @@ simplify_polynomial_list([L1|L2],L3) :-
     % There is nothing further to compute at this point
     !.
 
+%% polynomial_to_list(+P:polynomial, -L:List)
+%
+%  Converts a polynomial in a list.
+%  TODO: not everything is a +, there are -
+%
+polynomial_to_list(T1 + T2, L) :-
+    polynomial_to_list(T1, L1),
+    L = [T2|L1],
+    % The others computations are semantically meaningless
+    !.
+polynomial_to_list(P, L) :-
+    L = [P].
+%% Tests:
+%%?- polynomial_to_list(2*x^2+5+y*2, S).
+%@S = [y*2, 5, 2*x^2].
+
+%% list_to_polynomial(+P:polynomial, -L:List)
+%
+%  Converts a list in a polynomial.
+%  TODO: not everything is a +, there are -
+%
+list_to_polynomial([T1|T2], P) :-
+    list_to_polynomial(T2, L1),
+    (
+        not(L1 = []),
+        P = L1+T1
+    ;
+        P = T1
+    ),
+    % The others computations are semantically meaningless
+    !.
+list_to_polynomial(T, P) :-
+    P = T.
+%% Tests:
+%% TODO
+
+%% append_two_atoms_with_star(+V1, +V2, -R) is det
+%
+%  Returns R = V1 * V2
+%
+append_two_atoms_with_star(V1, V2, R) :-
+    term_string(V2, V3),
+    atom_concat(V1, *, V4),
+    atom_concat(V4, V3, S),
+    term_string(R, S).
+%% Tests:
+%  TODO
+
+%% scale_polynomial(+P:polynomial,+C:constant,-S:polynomial) is det
+%
+%  Scales a polynomial with a constant
+%
+scale_polynomial(P, C, S) :-
+    polynomial_to_list(P, L),
+    maplist(append_two_atoms_with_star(C), L, L2),
+    list_to_polynomial(L2, S).
+%simplify_polynomial(S1, S).
+
 %% monomial_parts(X, Y, Z)
 %
 %  TODO Maybe remove