c++ - Getting user input from R console: Rcpp and std::cin -

i have been doing exercises learn c++ , decided integrate them r since want write c++ backends r functions. having trouble finding solution retrieve user input r console. while there rcpp::rcout printing , returning output, there doesn't seem similar funciton std::cin....

#include <rcpp.h> // [[rcpp::export]] rcpp::string cola() {   rcpp::rcout << "pick drink:" << std::endl << "1 - espresso" << std::endl << "2 - americano" << std::endl << "3 - latte" << std::endl << "4 - cafe dopio" <<  std::endl << "5 - tea" << std::endl;   int drink;   std::cin >> drink;   std::string out;   switch(drink) {   case 1: out = "here espresso";   case 2: out = "here americano";   case 3: out = "here latte";   case 4: out = "here cafe dopio";   case 5: out = "here tea";   case 0: out = "error. choice not valid, here money back.";     break;   default:     if(drink > 5) {out = "error. choice not valid, here money back.";}   }   return out; } 

even without rcpp in mix, std::cin unsuitable interactive input.

to use r console rcpp, need use r functions (in particular, readline) instead of c++ functionality. luckily can pull r objects c++ code:

environment base = environment("package:base"); function readline = base["readline"]; function as_numeric = base["as.numeric"]; 

and can use them:

int drink = as<int>(as_numeric(readline("> "))); 

beware there's error in code: cases fall-through since missing break; furthermore, there’s no reason have case 0, , there’s no reason @ if in default case.

oh, , finally, don’t use std::endl unless need flush output (and need once here, @ end); use '\n' instead.