implementation of permutations in progress

permutation.cc

@@ -0,0 +1,68 @@
+/*
+    LA: linear algebra C++ interface library
+    Copyright (C) 2021 Jiri Pittner <jiri.pittner@jh-inst.cas.cz> or <jiri@pittnerovi.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "permutation.h"
+namespace LA {
+
+template <typename T>
+bool NRPerm<T>::is_valid() const
+{
+T n = this->size();
+if(n<0) return 0;
+NRVec_from1<T> used(n);
+used.clear();
+for(T i=1; i<=n; ++i)
+	{
+	T x= (*this)[i];
+	if(x<1||x>n) return 0;
+	used[x] += 1;
+	}
+for(T i=1; i<=n; ++i) if(used[i]!=1) return 0;
+return 1;
+}
+
+template <typename T>
+NRPerm<T> NRPerm<T>::inverse() const
+{
+NRPerm<T> q(this->size());
+for(T i=1; i<=this->size(); ++i) q[(*this)[i]]=i;
+return q;
+}
+
+
+template <typename T>
+NRPerm<T> NRPerm<T>::operator*(const NRPerm<T> q) const
+{
+T n=this->size();
+if(n!=q.size()) laerror("product of incompatible permutations");
+NRPerm<T> r(n);
+for(T i=1; i<=n; ++i) r[i] = q[(*this)[i]];
+return r;
+
+}
+
+
+
+
+
+
+/***************************************************************************//**
+ * forced instantization in the corresponding object file
+ ******************************************************************************/
+template class NRPerm<int>;
+}