#include <RcppArmadillo.h>
// [[Rcpp::depends(RcppArmadillo)]]

// [[Rcpp::export]]
arma::vec liml_omg_vapply(arma::mat& v1, arma::mat& omgi, arma::mat& v2) {
    arma::vec out(v1.n_rows);
    arma::mat res(1, 1);
    for (long i = 0; i < v1.n_rows; i++) {
        // works fine
        res = v1.row(i) * omgi * v2.row(i).t();
        out(i) = res(0, 0);
        // compile complains about it not being a function call
        out(i) = (v1.row(i) * omgi * v2.row(i).t())(0, 0);
    }
    return out;
}

// compiled in R returns:

file4d1578fe0fe7.cpp: In function ‘arma::vec liml_omg_vapply(arma::mat&, arma::mat&, arma::mat&)’:
file4d1578fe0fe7.cpp:16:61: error: no match for call to ‘(arma::enable_if2<true, const arma::Glue<arma::Glue<arma::subview_row<double>, arma::Mat<double>, arma::glue_times>, arma::Op<arma::subview_row<double>, arma::op_htrans>, arma::glue_times> >::result {aka const arma::Glue<arma::Glue<arma::subview_row<double>, arma::Mat<double>, arma::glue_times>, arma::Op<arma::subview_row<double>, arma::op_htrans>, arma::glue_times>}) (int, int)’
             out(i) = (v1.row(i) * omgi * v2.row(i).t())(0, 0);
                                                             ^
make: *** [file4d1578fe0fe7.o] Error 1
g++ -I/usr/share/R/include -DNDEBUG    -I"/home/james/R/x86_64-pc-linux-gnu-library/3.2/Rcpp/include" -I"/home/james/R/x86_64-pc-linux-gnu-library/3.2/RcppArmadillo/include" -I"/tmp/Rtmpsrp0A7"    -fpic  -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2 -g  -c file4d1578fe0fe7.cpp -o file4d1578fe0fe7.o
/usr/lib/R/etc/Makeconf:143: recipe for target 'file4d1578fe0fe7.o' failed
Error in sourceCpp(code = code, env = env, rebuild = rebuild, showOutput = showOutput,  :
  Error 1 occurred building shared library.