Correct some difficulties with parsing for model 3 and 4

ode.pl

@@ -54,6 +54,7 @@
     ode/3,
     ode_add_expression_to_molecule/2,
     ode_predicate/1,
+    remove_fraction/2,
     normalize_ode/1
   ]).
 
@@ -1336,7 +1337,7 @@ multiply_term(Num/Den, Denominator, NewNum) :-
 multiply_term(Num, Denominator, NewNum) :-
   mult_by(Num, Denominator, NewNum).
 
-mult_by(Num, [Head|Tail], NNum) :-
+mult_by(Num, [Head|Tail], NNum) :- !,
   mult_by(Num, Tail, NumTempo),
   distribute(NumTempo*Head, NNum).
 mult_by(Num, [], Num).
@@ -1366,11 +1367,11 @@ normalize_ode(NormalForm) :-
 normalize_expression(Expr + Term, ListVar, NExpr + NTerm) :- !,
   normalize_term(Term, ListVar, NTerm),
   normalize_expression(Expr, ListVar, NExpr).
-normalize_expression(Expr - Term, ListVar, NExpr + -1*NTerm) :- !,
-  normalize_term(Term, ListVar, NTerm),
+normalize_expression(Expr - Term, ListVar, NExpr + NTerm) :- !,
+  normalize_term(Term*(-1), ListVar, NTerm),
   normalize_expression(Expr, ListVar, NExpr).
-normalize_expression(-Term, ListVar, -1*NTerm) :- !,
-  normalize_term(Term, ListVar, NTerm).
+normalize_expression(-Term, ListVar, NTerm) :- !,
+  normalize_term(Term*(-1), ListVar, NTerm).
 normalize_expression(Term, ListVar, NTerm) :-
   normalize_term(Term, ListVar, NTerm).
 
@@ -1381,9 +1382,16 @@ normalize_term(Term, ListVar, NewTerm) :-
 
 %! filter_denominator(Term, Numerator, Denominator)
 
-filter_denominator(Term*X^N, Num, [X^Nm|Den]) :-
+filter_denominator(Term*X^N, Num, [NTerm|Den]) :-
   number(N), N<0, !,
   Nm is -N,
+  (
+    Nm = 1
+  ->
+    NTerm = X
+  ;
+    NTerm = X^Nm
+  ),
   filter_denominator(Term, Num, Den).
 filter_denominator(Term*X^N, [X^N|Num], Den) :- !,
   number(N), N>0, !,
@@ -1392,9 +1400,16 @@ filter_denominator(Term*X, [X|Num], Den) :- !,
   filter_denominator(Term, Num, Den).
 filter_denominator(Term/X, Num, [X|Den]) :- !,
   filter_denominator(Term, Num, Den).
-filter_denominator(X^N, [], [X^Nm]) :- !,
+filter_denominator(X^N, [], [NTerm]) :- !,
   number(N), N<0, !,
-  Nm is -N.
+  Nm is -N,
+  (
+    Nm = 1
+  ->
+    NTerm = X
+  ;
+    NTerm = X^Nm
+  ).
 filter_denominator(X, [X], []).
 
 

ode.plt

@@ -96,4 +96,12 @@ test(
   list_file_lines('test.tex', Lines),
   delete_file('test.tex').
 
+test(
+  'remove_fraction',[]) :-
+  remove_fraction(d(a)/dt = a/b, d(a)/dt = a),
+  remove_fraction(d(a)/dt = a/(b+c) + d, d(a)/dt = a + d*b + d*c),
+  remove_fraction(d(a)/dt = a/(b+c) + -1*d, d(a)/dt = a - d*b - d*c),
+  remove_fraction(d(a)/dt = a/b + c/d + e, d(a)/dt = a*d + c*b + e*b*d),
+  remove_fraction(d(a)/dt = a/b + c/d, d(a)/dt = a*d + c*b).
+
 :- end_tests(ode).