ence enables you to use classes and functions defined by the Rcpp package.</p></li>
<li><p><code>// [[Rcpp::export]]</code>：The function defined just below this sentence will be accessible from R. You need to attach this sentence to every function you want to use from R.</p></li>
<li><p><code>using namespace Rcpp;</code> : This sentence is optional. But if you did not write this sentence, you have to add the prefix <code>Rcpp::</code> to specify classes and functions defined by Rcpp. (For example, <code>R