Taylor questions

• Best way to achieve late-stage polymorphism
• numpy positive semi-definite warning
• improvement on tapply (shifting groups of vectors)
• libc++abi.dylib: terminating with uncaught exception of type std::__1::system_error: mutex lock failed: Invalid argument
• correctly registering a plugin to use Eigen via Rcpp
• product enum class in c++
• R function with no return value

Taylor answers