The functions in `src/prod.c' are from R-2.0.1 `src/main/array.c',
and are subject to the following copyrights: 

*  Copyright (C) 1998-2022   The R Core Team
*  Copyright (C) 2002-2015   The R Foundation
*  Copyright (C) 1995, 1996  Robert Gentleman and Ross Ihaka