Rcpp warning: Call to 'exp' is ambiguous

问题

I am writing a Rcpp code as below:

// [[Rcpp::depends(RcppArmadillo)]]
// [[Rcpp::depends(BH)]]
// [[Rcpp::plugins(cpp11)]]

#include <RcppArmadillo.h>
#include <boost/random.hpp>
#include <boost/random/uniform_real_distribution.hpp>
#include <math.h>

using namespace Rcpp;
using namespace std;

// [[Rcpp::export]]

 double ks(const double k, const double alpha, const double  mag, const double M0){
    double ksres;
    ksres=  k* std::exp ( alpha*(mag-M0) );
    return(ksres);
    }

But it shows that "Call to 'exp' is ambiguous". Why do I get this message and how will I solve it?

While I get in sessionInfo():

        R version 3.2.4 (2016-03-10)
        Platform: x86_64-apple-darwin13.4.0 (64-bit)
        Running under: OS X 10.12.6 (unknown)

locale:
[1] en_GB.UTF-8/en_GB.UTF-8/en_GB.UTF-8/C/en_GB.UTF-8/en_GB.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] Rcpp_0.12.4

loaded via a namespace (and not attached):
 [1] colorspace_1.2-6 scales_0.4.0     plyr_1.8.3       tools_3.2.4       inline_0.3.14    gtable_0.2.0     rstan_2.9.0-3   
 [8] gridExtra_2.2.1  ggplot2_2.1.0    grid_3.2.4       munsell_0.4.3    stats4_3.2.4

回答1:

I suggest this to be closed or deleted by OP. The question simply exhibits some allowed-but-not-recommended C++ usage:

extra headers included: the math headers are already brought in by Rcpp (which is brought in by RcppArmadillo)
you never ever need both cmath and math.h, and as stated here you do not need either
we generally recommend against flattening all namespaces unconditionally

With this, your code looks like this (still containing a call for C++11 which is not used, but does no harm):

// [[Rcpp::depends(RcppArmadillo)]]
// [[Rcpp::depends(BH)]]
// [[Rcpp::plugins(cpp11)]]

#include <RcppArmadillo.h>
#include <boost/random.hpp>
#include <boost/random/uniform_real_distribution.hpp>

// [[Rcpp::export]]
double ks(const double k, const double alpha, const double  mag, const double M0){
    double ksres;
    ksres=  k* std::exp ( alpha*(mag-M0) );
    return(ksres);
}

/*** R
ks(1.0, 2.0, 3.0, 4.0)
*/

This compiles without any warning whatsoever on my box (with stringent compiler warnings turned on, output not shown here) and runs as expected too:

R> Rcpp::sourceCpp("/tmp/soQ.cpp")

R> ks(1.0, 2.0, 3.0, 4.0)
[1] 0.135335
R>

来源：https://stackoverflow.com/questions/46646986/rcpp-warning-call-to-exp-is-ambiguous

标签

c++

rcpp