X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=blobdiff_plain;f=ginac%2Finifcns.cpp;h=03acbc7f2f42d4c221905652a39b21cdd3e041e2;hp=3bf0b2f7e9b93554c9344d357e848be1c9ba4aa3;hb=2700b3fa9c3a81236e8ceccb6aa9d5ea5848a1a0;hpb=d58aba5750e206575895725df80b65d907196928

diff --git a/ginac/inifcns.cpp b/ginac/inifcns.cpp
index 3bf0b2f7..03acbc7f 100644
--- a/ginac/inifcns.cpp
+++ b/ginac/inifcns.cpp
@@ -510,19 +510,74 @@ ex lsolve(const ex &eqns, const ex &symbols)
 }
 
 /** non-commutative power. */
-ex ncpower(const ex &basis, unsigned exponent)
+ex ncpow(const ex & basis, unsigned exponent)
 {
-	if (exponent==0) {
+	if (exponent == 0)
 		return _ex1();
-	}
 
 	exvector v;
 	v.reserve(exponent);
-	for (unsigned i=0; i<exponent; ++i) {
+	for (unsigned i=0; i<exponent; ++i)
 		v.push_back(basis);
+
+	return ncmul(v, true);
+}
+
+// Symmetrize/antisymmetrize over a vector of objects
+static ex symm(const ex & e, exvector::const_iterator first, exvector::const_iterator last, bool asymmetric)
+{
+	// Need at least 2 objects for this operation
+	int num = last - first;
+	if (num < 2)
+		return e;
+
+	// Sort object vector, transform it into a list, and make a copy so we
+	// will know which objects get substituted for which
+	exlist iv_lst;
+	iv_lst.insert(iv_lst.begin(), first, last);
+	shaker_sort(iv_lst.begin(), iv_lst.end(), ex_is_less());
+	lst orig_lst(iv_lst);
+
+	// Loop over all permutations (the first permutation, which is the
+	// identity, is unrolled)
+	ex sum = e;
+	while (next_permutation(iv_lst.begin(), iv_lst.end(), ex_is_less())) {
+		ex term = e.subs(orig_lst, lst(iv_lst));
+		if (asymmetric) {
+			exlist test_lst = iv_lst;
+			term *= permutation_sign(test_lst.begin(), test_lst.end(), ex_is_less());
+		}
+		sum += term;
 	}
+	return sum / factorial(numeric(num));
+}
+
+ex symmetrize(const ex & e, exvector::const_iterator first, exvector::const_iterator last)
+{
+	return symm(e, first, last, false);
+}
 
-	return ncmul(v,1);
+ex antisymmetrize(const ex & e, exvector::const_iterator first, exvector::const_iterator last)
+{
+	return symm(e, first, last, true);
+}
+
+ex symmetrize(const ex & e, const lst & l)
+{
+	exvector v;
+	v.reserve(l.nops());
+	for (unsigned i=0; i<l.nops(); i++)
+		v.push_back(l.op(i));
+	return symm(e, v.begin(), v.end(), false);
+}
+
+ex antisymmetrize(const ex & e, const lst & l)
+{
+	exvector v;
+	v.reserve(l.nops());
+	for (unsigned i=0; i<l.nops(); i++)
+		v.push_back(l.op(i));
+	return symm(e, v.begin(), v.end(), true);
 }
 
 /** Force inclusion of functions from initcns_gamma and inifcns_zeta