class that returns exponential distributed numbers (f=exp(-x) for x>0, 0 otherwise)
Tango Dual License: 3-Clause BSD License / Academic Free License v3.0. See LICENSE_TANGO.txt for details.
Copyright (c) 2008. Fawzi Mohamed Some parts copyright (c) 2009-2016 dunnhumby Germany GmbH. All rights reserved.
Initial release: July 2008