// Copyright (C) 2012 Davis E. King (davis@dlib.net) // License: Boost Software License See LICENSE.txt for the full license. #ifndef DLIB_NUM_NONNEGATIVE_WEIGHtS_Hh_ #define DLIB_NUM_NONNEGATIVE_WEIGHtS_Hh_ #include "../enable_if.h" namespace dlib { namespace impl2 { template < typename T, unsigned long (T::*funct)()const > struct hnnf_helper { typedef char type; }; template <typename T> char has_num_nonnegative_weights_helper( typename hnnf_helper<T,&T::num_nonnegative_weights>::type = 0 ) { return 0;} struct two_bytes { char a[2]; }; template <typename T> two_bytes has_num_nonnegative_weights_helper(int) { return two_bytes();} template <typename T> struct work_around_visual_studio_bug { const static unsigned long U = sizeof(has_num_nonnegative_weights_helper<T>('a')); }; // This is a template to tell you if a feature_extractor has a num_nonnegative_weights function or not. template <typename T, unsigned long U = work_around_visual_studio_bug<T>::U > struct has_num_nonnegative_weights { static const bool value = false; }; template <typename T> struct has_num_nonnegative_weights <T,1> { static const bool value = true; }; } // call fe.num_nonnegative_weights() if it exists, otherwise return 0. template <typename feature_extractor> typename enable_if<impl2::has_num_nonnegative_weights<feature_extractor>,unsigned long>::type num_nonnegative_weights ( const feature_extractor& fe ) { return fe.num_nonnegative_weights(); } template <typename feature_extractor> typename disable_if<impl2::has_num_nonnegative_weights<feature_extractor>,unsigned long>::type num_nonnegative_weights ( const feature_extractor& /*fe*/ ) { return 0; } } #endif // DLIB_NUM_NONNEGATIVE_WEIGHtS_Hh_