X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=blobdiff_plain;f=ginac%2Ftensor.cpp;h=28a7d7bf61b7d8831ce8c3c312b4027668c49b73;hp=65c8b59577c6e2cf0b20ebca8ad5e1fd9dee11dd;hb=c4c7b40ea71dd20ecc8942f9cab50c4bb9766624;hpb=c8382619f13fe586e8281b128404662f691ad4d8

diff --git a/ginac/tensor.cpp b/ginac/tensor.cpp
index 65c8b595..28a7d7bf 100644
--- a/ginac/tensor.cpp
+++ b/ginac/tensor.cpp
@@ -30,6 +30,7 @@
 #include "relational.h"
 #include "lst.h"
 #include "numeric.h"
+#include "matrix.h"
 #include "print.h"
 #include "archive.h"
 #include "utils.h"
@@ -493,6 +494,31 @@ again:
 	return false;
 }
 
+/** Contraction of epsilon tensor with something else. */
+bool tensepsilon::contract_with(exvector::iterator self, exvector::iterator other, exvector & v) const
+{
+	GINAC_ASSERT(is_ex_of_type(*self, indexed));
+	GINAC_ASSERT(is_ex_of_type(*other, indexed));
+	GINAC_ASSERT(is_ex_of_type(self->op(0), spinmetric));
+	unsigned num = self->nops() - 1;
+
+	if (is_ex_exactly_of_type(other->op(0), tensepsilon) && num+1 == other->nops()) {
+
+		// Contraction of two epsilon tensors is a determinant
+		ex dim = ex_to<idx>(self->op(1)).get_dim();
+		matrix M(num, num);
+		for (int i=0; i<num; i++)
+			for (int j=0; j<num; j++)
+				M(i, j) = delta_tensor(self->op(i+1), other->op(j+1));
+		int sign = minkowski ? -1 : 1;
+		*self = sign * M.determinant().simplify_indexed();
+		*other = _ex1();
+		return true;
+	}
+
+	return false;
+}
+
 //////////
 // global functions
 //////////