Additional transformations for mul and power [Sheplyakov].

[ginac.git] / ginac / mul.cpp

diff --git a/ginac/mul.cpp b/ginac/mul.cpp
index 9bbcd611f697df3bdaf87884616845aec9948e84..b4ef8972920d96b6f5b5043ba5ed404d8d561522 100644 (file)
--- a/ginac/mul.cpp
+++ b/ginac/mul.cpp
@@ -446,9 +446,62 @@ ex mul::eval(int level) const
                }
                return (new add(distrseq,
                                ex_to<numeric>(addref.overall_coeff).
-                               mul_dyn(ex_to<numeric>(overall_coeff))))
-                     ->setflag(status_flags::dynallocated | status_flags::evaluated);
+                               mul_dyn(ex_to<numeric>(overall_coeff)))
+                      )->setflag(status_flags::dynallocated | status_flags::evaluated);
+       } else if (seq_size >= 2) {
+               // Strip the content and the unit part from each term. Thus
+               // things like (-x+a)*(3*x-3*a) automagically turn into - 3*(x-a)2
+
+               epvector::const_iterator last = seq.end();
+               epvector::const_iterator i = seq.begin();
+               while (i!=last) {
+                       if (! (is_a<add>(i->rest) && i->coeff.is_equal(_ex1))) {
+                               // power::eval has such a rule, no need to handle powers here
+                               ++i;
+                               continue;
+                       }
+
+                       // XXX: What is the best way to check if the polynomial is a primitive? 
+                       numeric c = i->rest.integer_content();
+                       const numeric& lead_coeff =
+                               ex_to<numeric>(ex_to<add>(i->rest).seq.begin()->coeff).div_dyn(c);
+                       const bool canonicalizable = lead_coeff.is_integer();
+
+                       // XXX: The main variable is chosen in a random way, so this code 
+                       // does NOT transform the term into the canonical form (thus, in some
+                       // very unlucky event it can even loop forever). Hopefully the main
+                       // variable will be the same for all terms in *this
+                       const bool unit_normal = lead_coeff.is_pos_integer();
+                       if ((c == *_num1_p) && ((! canonicalizable) || unit_normal)) {
+                               ++i;
+                               continue;
+                       }
+
+                       std::auto_ptr<epvector> s(new epvector);
+                       s->reserve(seq.size());
+
+                       epvector::const_iterator j=seq.begin();
+                       while (j!=i) {
+                               s->push_back(*j);
+                               ++j;
+                       }
+
+                       if (! unit_normal) {
+                               c = c.mul(*_num_1_p);
+                       }
+                       const ex primitive = (i->rest)/c;
+                       s->push_back(expair(primitive, _ex1));
+                       ++j;
+
+                       while (j!=last) {
+                               s->push_back(*j);
+                               ++j;
+                       }
+                       return (new mul(s, ex_to<numeric>(overall_coeff).mul_dyn(c))
+                              )->setflag(status_flags::dynallocated);
+               }
        }
+
        return this->hold();
 }