contraction of symmetric with antisymmetric tensor over more than one index

[ginac.git] / ginac / indexed.cpp

diff --git a/ginac/indexed.cpp b/ginac/indexed.cpp
index f5c53a6bb956e6606b125c80a248c840840cb809..27379fec258572b7cc8606a8dc0875e7071d53e6 100644 (file)
--- a/ginac/indexed.cpp
+++ b/ginac/indexed.cpp
@@ -330,10 +330,20 @@ ex indexed::eval(int level) const
        if (level > 1)
                return indexed(symmetry, evalchildren(level));
 
+       const ex &base = seq[0];
+
        // If the base object is 0, the whole object is 0
-       if (seq[0].is_zero())
+       if (base.is_zero())
                return _ex0();
 
+       // If the base object is a product, pull out the numeric factor
+       if (is_ex_exactly_of_type(base, mul) && is_ex_exactly_of_type(base.op(base.nops() - 1), numeric)) {
+               exvector v = seq;
+               ex f = ex_to_numeric(base.op(base.nops() - 1));
+               v[0] = seq[0] / f;
+               return f * thisexprseq(v);
+       }
+
        // Canonicalize indices according to the symmetry properties
        if (seq.size() > 2 && (symmetry != unknown && symmetry != mixed)) {
                exvector v = seq;
@@ -347,7 +357,7 @@ ex indexed::eval(int level) const
        }
 
        // Let the class of the base object perform additional evaluations
-       return seq[0].bp->eval_indexed(*this);
+       return base.bp->eval_indexed(*this);
 }
 
 ex indexed::thisexprseq(const exvector & v) const
@@ -638,6 +648,16 @@ try_again:
                                }
                        }
 
+                       // Contraction of symmetric with antisymmetric object is zero
+                       if ((ex_to_indexed(*it1).symmetry == indexed::symmetric &&
+                            ex_to_indexed(*it2).symmetry == indexed::antisymmetric
+                         || ex_to_indexed(*it1).symmetry == indexed::antisymmetric &&
+                            ex_to_indexed(*it2).symmetry == indexed::symmetric)
+                        && dummy.size() > 1) {
+                               free_indices.clear();
+                               return _ex0();
+                       }
+
                        // Try to contract the first one with the second one
                        bool contracted = it1->op(0).bp->contract_with(it1, it2, v);
                        if (!contracted) {
@@ -669,13 +689,21 @@ try_again:
        }
        find_free_and_dummy(un.begin(), un.end(), free_indices, dummy_indices);
 
+       ex r;
        if (something_changed) {
                if (non_commutative)
-                       return ncmul(v);
+                       r = ncmul(v);
                else
-                       return mul(v);
+                       r = mul(v);
        } else
-               return e;
+               r = e;
+
+       // Product of indexed object with a scalar?
+       if (is_ex_exactly_of_type(r, mul) && r.nops() == 2
+        && is_ex_exactly_of_type(r.op(1), numeric) && is_ex_of_type(r.op(0), indexed))
+               return r.op(0).op(0).bp->scalar_mul_indexed(r.op(0), ex_to_numeric(r.op(1)));
+       else
+               return r;
 }
 
 /** Simplify indexed expression, return list of free indices. */
@@ -695,15 +723,27 @@ ex simplify_indexed(const ex & e, exvector & free_indices, const scalar_products
        // Simplification of sum = sum of simplifications, check consistency of
        // free indices in each term
        if (is_ex_exactly_of_type(e_expanded, add)) {
+               bool first = true;
                ex sum = _ex0();
+               free_indices.clear();
 
                for (unsigned i=0; i<e_expanded.nops(); i++) {
                        exvector free_indices_of_term;
-                       sum += simplify_indexed(e_expanded.op(i), free_indices_of_term, sp);
-                       if (i == 0)
-                               free_indices = free_indices_of_term;
-                       else if (!indices_consistent(free_indices, free_indices_of_term))
-                               throw (std::runtime_error("simplify_indexed: inconsistent indices in sum"));
+                       ex term = simplify_indexed(e_expanded.op(i), free_indices_of_term, sp);
+                       if (!term.is_zero()) {
+                               if (first) {
+                                       free_indices = free_indices_of_term;
+                                       sum = term;
+                                       first = false;
+                               } else {
+                                       if (!indices_consistent(free_indices, free_indices_of_term))
+                                               throw (std::runtime_error("simplify_indexed: inconsistent indices in sum"));
+                                       if (is_ex_of_type(sum, indexed) && is_ex_of_type(term, indexed))
+                                               sum = sum.op(0).bp->add_indexed(sum, term);
+                                       else
+                                               sum += term;
+                               }
+                       }
                }
 
                return sum;