diff --git a/polymani.pl b/polymani.pl
index a0f109b..4893bc9 100644
--- a/polymani.pl
+++ b/polymani.pl
@@ -33,6 +33,13 @@
  */
 :- use_module(library(clpr)).
 
+/*
+ * The porter_stem library implements the stemming algorithm described by
+ * Porter in Porter, 1980, ``An algorithm for suffix stripping''.
+ * The library also includes a functional tokenizer
+*/
+:- use_module(library(porter_stem)).
+
                  /*******************************
                  *              NLP             *
                  *******************************/
@@ -48,10 +55,11 @@ polyplay :-
     read_line_to_codes(user_input, InCodes),
     %% Restore old prompt
     prompt(_, OldPrompt),
-    %% Split the input at spaces and ignore \r and \t
-    split_string(InCodes, " ", "\r\t", LS),
-    %% Convert each set of codes into a term or atom, as appropriate
-    maplist(name, LA, LS),
+    %% Use the porter_stem library to tokenize the input
+    %% This does more than splitting at the spaces, such as
+    %% splitting at operators. Aditionally, gives
+    %% atoms already and handles 'P1' well
+    tokenize_atom(InCodes, LA),
     (
         %% If we read a 'bye', terminate
         LA == [bye],
@@ -310,6 +318,12 @@ print_all_stored_variables([]).
 %
 %  Flatten a polynomail tree into a simple polynomial
 %
+polynomial_tree_to_polynomial(op(neg, T), P1) :-
+    %% If it matched on the version with a node, don't go back
+    !,
+    %% Delegate
+    polynomial_tree_to_polynomial(T, P),
+    atom_concat('-', P, P1).
 polynomial_tree_to_polynomial(op(Op, TL, TR), P) :-
     %% If it matched on the version with a node, don't go back
     !,
@@ -470,6 +484,7 @@ parse_floating_number(TN) -->
 %@ TN = op('.', 2, 4).
 %% ?- parse_floating_number(TN, [negative, two, dot, 4], _).
 %@ TN = op('.', op(neg, 2), 4).
+%@ TN = op('.', op(neg, 2), 4).
 
 %% parse_positive_integer_number(-tree, +stream, -not_consumed) is det
 %
@@ -495,7 +510,7 @@ parse_integer_number(N) -->
 parse_integer_number(op(neg, T)) -->    % TODO
     %% A number can start with "negative", to negate it
     [negative],
-    parse_number_explicit(void, void, T).
+    parse_integer_number(T).
 parse_integer_number(T) -->
     parse_number_explicit(void, void, T).
 %% Tests: