rexp.h

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// -*- mode: C++; c-indent-level: 4; c-basic-offset: 4; tab-width: 4 -*-
//
// rexp.h: Rcpp R/C++ interface class library -- 
//
// Copyright (C) 2010 - 2011 Douglas Bates, Dirk Eddelbuettel and Romain Francois
//
// This file is part of Rcpp.
//
// Rcpp 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.
//
// Rcpp 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 Rcpp.  If not, see <http://www.gnu.org/licenses/>.

#ifndef Rcpp__stats__random_rexp_h
#define Rcpp__stats__random_rexp_h

namespace Rcpp {
        namespace stats {

                class ExpGenerator : public ::Rcpp::Generator<false,double> {
                public:
        
                        ExpGenerator( double scale_ ) : scale(scale_) {}
        
                        inline double operator()() const {
                                return scale * exp_rand() ;
                        }
        
                private:
                        double scale ;
                } ;

        } // stats

        // Please make sure you to read Section 6.3 of "Writing R Extensions"
        // about the need to call GetRNGstate() and PutRNGstate() when using 
        // the random number generators provided by R.
        inline NumericVector rexp( int n, double rate ){
                double scale = 1.0 / rate ;
                if (!R_FINITE(scale) || scale <= 0.0) {
                        if(scale == 0.) return NumericVector( n, 0.0 ) ;
                        /* else */
                        return NumericVector( n, R_NaN ) ;
                }
                if( scale == 1.0 )
                        return NumericVector( n, ::exp_rand ) ;
                return NumericVector( n, stats::ExpGenerator( scale ) ) ;
        }
        inline NumericVector rexp( int n){
                return NumericVector( n, ::exp_rand ) ;
        }

}

#endif