How to calling R code from C++ - rcpp

Question

I try to include R-code in C++ (Qt creator). To get familiar with the packages Rcpp, RInside and the R-source code R-3.0.1 I try to run the following example:
#include <QCoreApplication>
#include<iostream>
#include<Rcpp.h>
#include <RInside.h> // for the embedded R via RInside
int main(int argc, char *argv[]) {
RInside R(argc, argv); // create an embedded R instance
R["txt"] = "Hello, world!\n"; // assign a char* (string) to 'txt'
R.parseEvalQ("cat(txt)"); // eval the init string, ignoring any returns
exit(0);
}
First Question:
The file string.h comes from the package Rcpp, but it always generates a lots (130!) errors like:
'internal does not name a type'
'StringProxy does not name a type etc.
What is wrong with it?
Second Question:
In the .pro file I have to include all subfolder of the packages separatly like:
INCLUDEPATH += "W:\hesm\Private\Private\Qt files\ConnectToR\Rcpp\include\Rcpp\module"
Is it possible to include a folder (package) with all its subfolders in one quote?
Thanks

Answer 1

You are doing it wrong. The code you quote is verbatim from the examples/standards/rinside_sample0.cpp file of the RInside package.
It so happens that there is also a complete Qt example in examples/qt/ directory (albeit building a Qt application rather than a command-line one). You are expected to do
qmake && make
and the binary is built --- because all the required logic is in the .pro file.
Your question really is about how to use Qt Creator / Qt build tools, and has nothing to do with Rcpp or RInside per se.
Our supplied examples all work as documented and expected. Build them, look at what make executes and infer what you need for your use with Qt Creator (which is a fine tool, but not one supported by R out of the box). If you want to use it, you need to adapt to it locally.