Make use of the Preview tab just above!

• searched the mailing list archives for the rcpp-devel list for the question you want to ask about; you can do this at at Google with the site: qualifier as in this simple example: site:lists.r-forge.r-project.org rcpp-devel how do I declare a const vector;

• searched the StackOverflow [rcpp] tag e.g. via [rcpp] how do I sample a vector;

• searched existing GitHub issues which can be searched among open and closed ones;

• read the Contributing page for details on preferred reporting and style;

If you have the above, remove the text above and provide a Minimally Complete and Verifiable Example (MCVE), the output of sessionInfo() plus relevant information about the C++ compiler. All this takes a little bit of effort---but greatly increases your chances of getting an applicable and helpful follow-up in return.