I am fitting a model that requires a call to `algebra_solver`

. After including the call to `algebra_solver(system, guess, theta, x_r, x_i);`

, the code fails to compile.

In order to test the code, I replaced the value that would be returned by algebra_solver with a constant. With the call to algebra_solver removed, the code compiles and runs (but obviously does not converge to anything).

I am wondering whether I need to write some wrapper for this function in a separate .hpp file? If so, it would be great if you could provide a little guidance.

The error message is as follows:

```
Error in compileCode(f, code, language = language, verbose = verbose) :
Compilation ERROR, function(s)/method(s) not created! file1f41285cda55.cpp:6:36: warning: ISO C++11 requires whitespace after the macro name
#define STAN__SERVICES__COMMAND_HPP#include <boost/integer/integer_log2.hpp>
^
In file included from /usr/lib64/R/library/RcppEigen/include/Eigen/Core:392,
from /usr/lib64/R/library/RcppEigen/include/Eigen/Dense:1,
from /home/grad/hs182/R/x86_64-redhat-linux-gnu-library/3.6/StanHeaders/include/stan/math/prim/mat/fun/Eigen.hpp:13,
from <command-line>:
/usr/lib64/R/library/RcppEigen/include/Eigen/src/Core/arch/SSE/PacketMath.h:60:39: warning: ignoring attributes on template argument ‘__m128’ {aka ‘__vector(4) float’} [-Wignored-attributes]
template<> struct is_arithmetic<__m128> { enum { value = true }; };
^
/usr/lib64/R/library/RcppEigen/include/Eigen/src/Core/arch/SSE/PacketMath.h:61:40: warning: ignori
```

Thank you!