internally used rate function from optiRum::RATE written in C++

C++rate

library(Rcpp)
cppFunction('double rate(double nper, double pmt, double pv){
            float rate1 = 0.01 ;
            float rate2 = 0.05 ;
            float newrate = 0 ;
int n = 10;
for (int i = 0; i < n; ++i) {
            double pv1 = floor((-pmt/rate1 * (1 - 1/pow((1 + rate1),nper)))*100+0.5)/100 - pv ;
            double pv2 = floor((-pmt/rate2 * (1 - 1/pow((1 + rate2),nper)))*100+0.5)/100 - pv ;
            if (pv1 != pv2) {
               newrate = (pv1 * rate2 - pv2 * rate1)/(pv1 - pv2) ;
            }
            if (abs(pv1) > abs(pv2)) {
                rate1 = newrate ; 
            }
            else {
                rate2 = newrate ; 
            }
        }
        return rate1;
            }')
rate(12,-500,3000)