From 93a43cde52e1ca1ff02d952e31c5b24081da65a0 Mon Sep 17 00:00:00 2001
From: Hugo Sales <hdcs333@gmail.com>
Date: Sat, 17 Nov 2018 23:53:49 +0000
Subject: [PATCH] Progess...

---
 polimani.pl | 95 +++++++++++++++++++++++++++++++++--------------------
 1 file changed, 59 insertions(+), 36 deletions(-)

diff --git a/polimani.pl b/polimani.pl
index fd62f7c..0d13087 100644
--- a/polimani.pl
+++ b/polimani.pl
@@ -1,3 +1,4 @@
+%% -*- mode: prolog-*-
 %% Follows 'Coding guidelines for Prolog' - Theory and Practice of Logic Programming
 %% https://doi.org/10.1017/S1471068411000391
 
@@ -10,12 +11,6 @@ power_p(X) :-
 power_p(X^N) :-
     polynomial_variable_p(X), integer(N), N > 1, !.
 
-%% coefficient_p(K) :-
-%%     number(K).
-
-%% term_p(X) :-
-%%     polynomial_variable_p(X), !.
-
 term_p(N) :-
     number(N).
 term_p(X) :-
@@ -27,7 +22,7 @@ term_p(L * R) :-
 polynomial_p(M) :-
     term_p(M).
 polynomial_p(L + R) :- 		% Left greedy
-    polynomial_p(L), !,		% Why?
+    polynomial_p(L),		% Why?
     term_p(R), !.
 
 %% ?- polynomial_p(3*x^2+y*z).
@@ -40,60 +35,88 @@ polynomial_p(L + R) :- 		% Left greedy
 %@ false.
 %% ?- polynomial_p(3*x^2+y*z+x^100*y*z).
 %@ true.
-%@ true .
-%@ false.
-%@ false.
-%@ false.
-%@ false.
+%@ true.
+%% @ false. WIP
 
 simplify_term(1 * P, P) :-
     term_p(P), !.
 simplify_term(0 * _, 0) :-
     !.
-simplify_term(T, S) :-
+simplify_term(T, T2) :-
     term_to_list(T, L),
-    sort(L, L2),
-    join_like_terms(L2, S).
+    sort(0, @=<, L, L2),
+    join_like_terms(L2, L3),
+    sort(0, @>=, L3, L4),
+    term_to_list(T2, L4).
 
 %% ?- simplify_term(2*y*z*x^3*x, X).
+%@ X = [z^1, y^1, x^4, 2].
+%@ false.
+%@ X = [2, x^4, y^1, z^1].
 %@ X = [2, x^1, x^3, y^1, z^1].
+%% ?- simplify_term(2*y*z*23*x*y*x^3*x, X).
+%@ X = [2, 23, x^1, x^3, y^1, z^1].
+%@ X = [46, x^4, y^1, z^1].
 
-join_like_terms([T1, T2 | L], [P^N | L]) :-
-    P^N1 is T,
-    P^N2 is T2,
+join_like_terms([T1, T2 | L], [B1^N | L2]) :-
+    not(number(T1)),
+    not(number(T2)),
+    B1^N1 = T1,
+    B2^N2 = T2,
+    B1 == B2,
+    join_like_terms(L, L2),
     N is N1 + N2,
     !.
-join_like_terms([N1, N2 | L], [N | L]) :-
+join_like_terms([N1, N2 | L], [N | L2]) :-
+    number(N1),
+    number(N2),
     N is N1 * N2,
+    join_like_terms(L, L2),
     !.
-join_like_terms(T, T).
-
+join_like_terms([X | L], [X | L2]) :-
+    join_like_terms(L, L2).
+join_like_terms([], []).
 %% ?- join_like_terms([2, 3, x^1, x^2], T).
-%@ ERROR: Arguments are not sufficiently instantiated
-%@ ERROR: In:
-%@ ERROR:    [9] _3138^_3140 is _3134
-%@ ERROR:    [8] join_like_terms([2,3|...],[_3188^_3190,...|...]) at /tmp/ediprologODLYxF:62
-%@ ERROR:    [7] <user>
-%@    Exception: (8) join_like_terms([2, 3, x^1, x^2], _2428) ? abort
-%@ % Execution Aborted
-%@ T = [6, x^1, x^2].
-%@ T = [6, x^1].
-%@ T = [6].
-%@ T = [2].
+%@ T = [6, x^3].
+%@ T = [6, x^3].
+%% ?- join_like_terms([2, 3, x^1, x^2, y^1, y^6], T).
+%@ T = [6, x^3, y^7].
+%@ T = [6, x^3, y].
 
 term_to_list(L * N, [N | TS]) :-
     number(N),
-    term_to_list(L, TS), !.
+    term_to_list(L, TS),
+    !.
 term_to_list(L * T, [T2 | TS]) :-
     power_p(T),
     power_to_canon(T, T2),
-    term_to_list(L, TS), !.
+    term_to_list(L, TS),
+    !.
 term_to_list(T, [T]).
 
+list_to_term([N | NS], N * L) :-
+    number(N),
+    term_to_list(L, NS).
+
+%% ?- term_to_list(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].
+%% ?- term_to_list(X, [2, x^1, y^1]).
+%@ X = y^1*x*2.
+%@ X = y^1*x*2.
+%@ X = y^1*x*2.
+%@ X = y*x*2.
+%@ X = x*2.
+%@ X = 2.
+%@ false.
+%@ false.
+%@ X = x*2.
+
 power_to_canon(T, T^1) :-
-    polynomial_variable_p(T).
+    polynomial_variable_p(T),
+    !.
 power_to_canon(T^N, T^N) :-
-    polynomial_variable_p(T).
+    polynomial_variable_p(T),
+    !.
 
 simplify_polynomial(M, M2) :-
     term_p(M), simplify_term(M, M2), !.