moved some common code to the 'tensor' class
authorChristian Bauer <Christian.Bauer@uni-mainz.de>
Mon, 8 Jul 2002 21:07:19 +0000 (21:07 +0000)
committerChristian Bauer <Christian.Bauer@uni-mainz.de>
Mon, 8 Jul 2002 21:07:19 +0000 (21:07 +0000)
ginac/tensor.cpp
ginac/tensor.h

index ccae243..48835ed 100644 (file)
@@ -318,15 +318,9 @@ ex tensepsilon::eval_indexed(const basic & i) const
        return i.hold();
 }
 
-/** Contraction of an indexed delta tensor with something else. */
-bool tensdelta::contract_with(exvector::iterator self, exvector::iterator other, exvector & v) const
+bool tensor::replace_contr_index(exvector::iterator self, exvector::iterator other) const
 {
-       GINAC_ASSERT(is_a<indexed>(*self));
-       GINAC_ASSERT(is_a<indexed>(*other));
-       GINAC_ASSERT(self->nops() == 3);
-       GINAC_ASSERT(is_a<tensdelta>(self->op(0)));
-
-       // Try to contract first index
+       // Try to contract the first index
        const idx *self_idx = &ex_to<idx>(self->op(1));
        const idx *free_idx = &ex_to<idx>(self->op(2));
        bool first_index_tried = false;
@@ -337,8 +331,8 @@ again:
                        const idx &other_idx = ex_to<idx>(other->op(i));
                        if (is_dummy_pair(*self_idx, other_idx)) {
 
-                               // Contraction found, remove delta tensor and substitute
-                               // index in second object
+                               // Contraction found, remove this tensor and substitute the
+                               // index in the second object
                                *self = _ex1;
                                *other = other->subs(other_idx == *free_idx);
                                return true;
@@ -348,7 +342,7 @@ again:
 
        if (!first_index_tried) {
 
-               // No contraction with first index found, try second index
+               // No contraction with the first index found, try the second index
                self_idx = &ex_to<idx>(self->op(2));
                free_idx = &ex_to<idx>(self->op(1));
                first_index_tried = true;
@@ -358,6 +352,19 @@ again:
        return false;
 }
 
+/** Contraction of an indexed delta tensor with something else. */
+bool tensdelta::contract_with(exvector::iterator self, exvector::iterator other, exvector & v) const
+{
+       GINAC_ASSERT(is_a<indexed>(*self));
+       GINAC_ASSERT(is_a<indexed>(*other));
+       GINAC_ASSERT(self->nops() == 3);
+       GINAC_ASSERT(is_a<tensdelta>(self->op(0)));
+
+       // Replace the dummy index with this tensor's other index and remove
+       // the tensor (this is valid for contractions with all other tensors)
+       return replace_contr_index(self, other);
+}
+
 /** Contraction of an indexed metric tensor with something else. */
 bool tensmetric::contract_with(exvector::iterator self, exvector::iterator other, exvector & v) const
 {
@@ -371,36 +378,9 @@ bool tensmetric::contract_with(exvector::iterator self, exvector::iterator other
        if (is_ex_of_type(other->op(0), tensdelta))
                return false;
 
-       // Try to contract first index
-       const idx *self_idx = &ex_to<idx>(self->op(1));
-       const idx *free_idx = &ex_to<idx>(self->op(2));
-       bool first_index_tried = false;
-
-again:
-       if (self_idx->is_symbolic()) {
-               for (unsigned i=1; i<other->nops(); i++) {
-                       const idx &other_idx = ex_to<idx>(other->op(i));
-                       if (is_dummy_pair(*self_idx, other_idx)) {
-
-                               // Contraction found, remove metric tensor and substitute
-                               // index in second object
-                               *self = _ex1;
-                               *other = other->subs(other_idx == *free_idx);
-                               return true;
-                       }
-               }
-       }
-
-       if (!first_index_tried) {
-
-               // No contraction with first index found, try second index
-               self_idx = &ex_to<idx>(self->op(2));
-               free_idx = &ex_to<idx>(self->op(1));
-               first_index_tried = true;
-               goto again;
-       }
-
-       return false;
+       // Replace the dummy index with this tensor's other index and remove
+       // the tensor (this is valid for contractions with all other tensors)
+       return replace_contr_index(self, other);
 }
 
 /** Contraction of an indexed spinor metric with something else. */
@@ -507,48 +487,6 @@ bool tensepsilon::contract_with(exvector::iterator self, exvector::iterator othe
                *self = sign * M.determinant().simplify_indexed();
                *other = _ex1;
                return true;
-
-       } else if (other->return_type() == return_types::commutative) {
-
-#if 0
-               // This handles eps.i.j.k * p.j * p.k = 0 and related cases.
-               // Actually, simplify_indexed() can handle most of them on its own
-               // but one specific case that is not covered there is
-               //   eps~mu.nu~i~j * p.mu * p~nu
-               // because of the difference in variance in the dummy indices mu
-               // and nu. Eventually, simplify_indexed() should be extended to
-               // handle this case, and this hack removed.
-               exvector c;
-
-               // Handle all indices of the epsilon tensor
-               for (int i=0; i<num; i++) {
-                       ex idx = self->op(i+1);
-
-                       // Look whether there's a contraction with this index
-                       exvector::const_iterator ait, aitend = v.end();
-                       for (ait = v.begin(); ait != aitend; ait++) {
-                               if (ait == self)
-                                       continue;
-                               if (is_a<indexed>(*ait) && ait->return_type() == return_types::commutative && ex_to<indexed>(*ait).has_dummy_index_for(idx) && ait->nops() == 2) {
-
-                                       // Yes, did we already have another contraction with the same base expression?
-                                       ex base = ait->op(0);
-                                       if (std::find_if(c.begin(), c.end(), bind2nd(ex_is_equal(), base)) == c.end()) {
-
-                                               // No, add the base expression to the list
-                                               c.push_back(base);
-
-                                       } else {
-
-                                               // Yes, the contraction is zero
-                                               *self = _ex0;
-                                               *other = _ex0;
-                                               return true;
-                                       }
-                               }
-                       }
-               }
-#endif
        }
 
        return false;
index cbe0a44..9b19dc1 100644 (file)
@@ -42,6 +42,13 @@ protected:
        // functions overriding virtual functions from base classes
 protected:
        unsigned return_type(void) const { return return_types::noncommutative_composite; }
+
+       // non-virtual functions in this class
+public:
+       /** Replace dummy index in contracted-with object by the contracting
+        *  object's second index (used internally for delta and metric tensor
+        *  contractions. */
+       bool replace_contr_index(exvector::iterator self, exvector::iterator other) const;
 };