That is supposed to work. If you add `LDFLAGS += --no-undefined`

to ~/.R/Makevars you get a slightly more informative error message (an a linker error rather than an error from `dyn.load`

) like:

```
file5e8d2fcaf228.o: In function `boost::math::tools::promote_args<double, float, float, float, float, float>::type model5e8d11fab598_discrete_power_law_namespace::power_law<double>(int const&, double const&, std::ostream*)':
file5e8d2fcaf228.cpp:(.text._ZN46model5e8d11fab598_discrete_power_law_namespace9power_lawIdEEN5boost4math5tools12promote_argsIT_fffffE4typeERKiRKS5_PSo[_ZN46model5e8d11fab598_discrete_power_law_namespace9power_lawIdEEN5boost4math5tools12promote_argsIT_fffffE4typeERKiRKS5_PSo]+0x2f): undefined reference to `boost::math::tools::promote_args<double, float, float, float, float, float>::type model5e8d11fab598_discrete_power_law_namespace::zeta<double>(double const&, std::ostream*)'
```

I don’t understand why it thinks it needs a definition of

`boost::math::tools::promote_args<double, float, float, float, float, float>::type blah_blah_namespace::zeta<double>(double const&, std::ostream*)`

as opposed to what is defined which is simply

```
double zeta(const double& s, std::ostream* pstream__) {
return boost::math::zeta(s);
}
```

And then it does it again for the var specialization

```
file5e8d2fcaf228.o: In function `boost::math::tools::promote_args<stan::math::var, float, float, float, float, float>::type model5e8d11fab598_discrete_power_law_namespace::power_law<stan::math::var>(int const&, stan::math::var const&, std::ostream*)':
file5e8d2fcaf228.cpp:(.text._ZN46model5e8d11fab598_discrete_power_law_namespace9power_lawIN4stan4math3varEEEN5boost4math5tools12promote_argsIT_fffffE4typeERKiRKS8_PSo[_ZN46model5e8d11fab598_discrete_power_law_namespace9power_lawIN4stan4math3varEEEN5boost4math5tools12promote_argsIT_fffffE4typeERKiRKS8_PSo]+0x109): undefined reference to `boost::math::tools::promote_args<stan::math::var, float, float, float, float, float>::type model5e8d11fab598_discrete_power_law_namespace::zeta<stan::math::var>(stan::math::var const&, std::ostream*)'
```