hello,
I would like to pass an integer as default VectorXi argument as function argument, so I would like to define the int as a vector of size 1.
I tried different things, for example comma initializer or

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void chk(Eigen::VectorXd a =  VectorXd::Constant(1, 1.0),
                    Eigen::VectorXi b =  VectorXi::Constant(1, 0)){
  cout << a.size() << " a is 1.0 = " << a << "  ";
  cout << b.size() << " b is 0 = " << b << endl;
}


for example but i get warnings

Warning messages:
1: Unable to parse C++ default value 'VectorXd::Constant(1, 1.0)' for argument a of function chk
2: Unable to parse C++ default value 'VectorXi::Constant(1, 0)' for argument b of function chk

passing

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chk(Eigen::VectorXd a =  1.0,  Eigen::VectorXi b =  0)


actually works, but what if I want to pass a vector with two elements?

Any help appreciated. Thanks, Marco

Your first example is perfectly fine, except that you're missing the Eigen:: namespace prefix.

Also, I guess that those warnings come from your IDE, and not from the compiler. In general don't believe to much in those warnings as IDE's parsers are rather limited regarding templates.

ggael wrote:Your first example is perfectly fine, except that you're missing the Eigen:: namespace prefix.

Also, I guess that those warnings come from your IDE, and not from the compiler. In general don't believe to much in those warnings as IDE's parsers are rather limited regarding templates.

Thanks ggael. Then the problem is not Eigen.
I should have specified I am using RcppEigen in Rstudio. Maybe it depends on that, it is difficult for me to now if thewarnings and errors come from the compiler. What happens is that it compiles giving warnings

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void chk(Eigen::VectorXd a = Eigen::VectorXd::Constant(2, 0.0),
                    Eigen::VectorXi b = Eigen::VectorXd::Constant(2, 1)){
  cout << a.size() << " a is 1.0 = " << a << "  ";
  cout << b.size() << " b is 0 = " << b << endl; 
}

and when I run chk() I get the following error

Error in chk() : argument "a" is missing, with no default

maybe i should ask the Rcpp community.

ah, right, this might rather be an issue with Rcpp.