Add Factorial helper

pkg/helpers/math.go

@@ -0,0 +1,24 @@
+// Copyright © 2020 Ettore Di Giacinto <mudler@gentoo.org>
+//
+// 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 2 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/>.
+
+package helpers
+
+func Factorial(n uint64) (result uint64) {
+	if n > 0 {
+		result = n * Factorial(n-1)
+		return result
+	}
+	return 1
+}