13 #ifndef MLPACK_CORE_DATA_EXTENSION_HPP    14 #define MLPACK_CORE_DATA_EXTENSION_HPP    21 inline std::string 
Extension(
const std::string& filename)
    23   const size_t ext = filename.rfind(
'.');
    24   std::string extension;
    25   if (ext == std::string::npos)
    28   extension = filename.substr(ext + 1);
    29   std::transform(extension.begin(), extension.end(), extension.begin(),
 Linear algebra utility functions, generally performed on matrices or vectors. 
 
The core includes that mlpack expects; standard C++ includes and Armadillo. 
 
std::string Extension(const std::string &filename)