From f6d562a34e1568cfd528c4cfb455fd1941586e12 Mon Sep 17 00:00:00 2001
From: Hugo Sales <hdcs333@gmail.com>
Date: Tue, 20 Nov 2018 16:14:53 +0000
Subject: [PATCH] Some improvements

---
 polimani.pl | 83 +++++++++++++++++++++++++++++++++--------------------
 1 file changed, 52 insertions(+), 31 deletions(-)

diff --git a/polimani.pl b/polimani.pl
index 75504ff..eedd134 100644
--- a/polimani.pl
+++ b/polimani.pl
@@ -19,25 +19,34 @@ 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 .
+%% ?- polynomial_variable(x).
+%@ true .
 
 %% power(+X:atom) is det
 %
 %  Returns true if X is a power term, false otherwise.
 %
-power(X) :-
-    polynomial_variable(X).
-power(X^N) :-
-    polynomial_variable(X),
+power(X ^ N) :-
+    %% X ^ N = P,
     integer(N),
-    N >= 1.
+    !,
+    %% write(N),
+    N >= 1,
+    polynomial_variable(X),
+    !.
+power(X) :-
+    polynomial_variable(X),
+    !.
 %% Tests:
 %% ?- power(x^1).
 %@ true .
-
+%% ?- power(x^(-3)).
+%@ false.
+%@ true.
+%@ -3
+%@ true .
 
 %% term(+N:atom) is det
 %
@@ -49,10 +58,12 @@ term(X) :-
     power(X).
 term(L * R) :-
     term(L),
-    term(R),
-    !.
+    term(R).
 %% Tests:
-%% TODO
+%% ?- term(2*x^3).
+%@ true .
+%% ?- term(x^(-3)).
+%@ true .
 
 %% is_term_valid_in_predicate(+T, +F) is det
 %
@@ -71,7 +82,8 @@ is_term_valid_in_predicate(T, F) :-
         fail
 ).
 %% Tests:
-%% ?- is_term_valid_in_predicate().
+%% ?- is_term_valid_in_predicate(1, "Foo").
+%@ true .
 
 %% polynomial(+M:atom) is det
 %
@@ -118,7 +130,8 @@ term_to_list(P, [P2]) :-
     power(P),
     power_to_canon(P, P2).
 %% Tests:
-%% ?- term_to_list(2*y*z*23*x*y*x^3*x, X).
+%% ?- term_to_list(1*2*y*z*23*x*y*x^3*x, X).
+%@ X = [x^1, x^3, y^1, x^1, 23, z^1, y^1, 2, 1] .
 %@ X = [x^1, x^3, y^1, x^1, 23, z^1, y^1, 2] .
 %% ?- term_to_list(X, [y^1, x^1]).
 %@ X = x*y .
@@ -128,28 +141,33 @@ term_to_list(P, [P2]) :-
 %% ?- term_to_list(X, [y^6, z^2, x^4]).
 %@ X = x^4*z^2*y^6 .
 
-%% simplify_term(+T:atom, -P) is det
+%% simplify_term(+Term_In:term, ?Term_Out:term) is det
 %
 %  Simplifies a term.
 %
-simplify_term(1 * P, P).
-simplify_term(0 * _, 0).
-simplify_term(T, T2) :-
-    term_to_list(T, L),
+simplify_term(Term_In, Term_Out) :-
+    term_to_list(Term_In, L),
     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).
+(
+    member(0, L2),
+    Term_Out = 0
+;
+    exclude(==(1), L2, L3),
+    join_like_terms(L3, L4),
+    sort(0, @>=, L4, L5),
+    term_to_list(Term_Out, L5)
+),
+    % First result is always the most simplified form.
+    !.
 %% Tests:
 %% ?- simplify_term(2*y*z*x^3*x, X).
-%@ X = 2*(x^4*(y*z)).
-%@ X = z*(y*(x^4*2)).
-%% ?- simplify_term(2*y*z*23*x*y*x^3*x, X).
-%@ X = 46*(x^2*(x^3*(y^2*z))).
-%@ X = z*(y^2*(x^3*(x^2*46))).
-%@ X = [2, 23, x^1, x^3, y^1, z^1].
-%@ X = [46, x^4, y^1, z^1].
+%@ X = 2*x^4*y*z.
+%% ?- simplify_term(1*y*z*x^3*x, X).
+%@ X = x^4*y*z.
+%% ?- simplify_term(0*y*z*x^3*x, X).
+%@ X = 0.
+%% ?- simplify_term(6*y*z*7*x*y*x^3*x, X).
+%@ X = 42*x^2*x^3*y^2*z.
 
 %% join_like_terms(+List, -List)
 %
@@ -209,7 +227,10 @@ simplify_polynomial(P + M, P2 + M2) :-
     simplify_polynomial(P, P2),
     simplify_term(M, M2).
 %% Tests:
-%% TODO
+%% ?- simplify_polynomial(1, 1).
+%@ Invalid term in simplify_polynomial(M, M2): 1
+%@ false.
+
 
 %% simplify_polynomial_list(+L1,-L3) is det
 %