template-meta-programming

Is it possible to get at the offset of a mpl::vector after performing a mpl::find<seq,type> on it ? Put differently I want to do the compile time equavalent of: #include <vector> #include <algorithm> #include <iostream> int main() { typedef std::vector<int> v_type; v_type v_int(3); v_int[0] = 1; v_int[1] = 2; v_int[2] = 3; v_type::iterator it= std::find( v_int.begin() ,v_int.end(),3); std::cout << it - v_int.begin() << std::endl; } Failing this, my types in mpl::vector have a type_trait<T>::ordinal const hard-coded, I would like to avoid this if possible. Important Note , I am also creating a

Inspired by this question , i'm wondering if there is some compile-time check one can introduce to detect if two given template instantiations: template <typename T> class Templ... typedef Templ<std::string> stringInstance; typedef Templ<double> doubleInstance; are constructed from the same definition, or if they are built from different specializations of the Templ template so basically the hypothetical template function will behave like this: template <typename T> class Templ {} template <> class Templ<std::string> {} template <> class Templ<double> {} template <typename T1,typename T2>

I want to define an operator<< for all enums, to cout the value and print that it is an enum like this: code: enum AnyEnum{A,B,C}; AnyEnum enm = A; cout << enm <<endl; output: This is an enum which has a value equal to 0 I know a way of doing this with Boost library by using is_enum struct. But I don’t understand how it works. So that's why, in general, I am interested how to identify if the veriable is a class type, union type or an enum (in compile time). Determining class types you could use the fact that member pointers exist template<typename A, typename B> struct issame { }; template

Clarifiration: How do I Edit and Save Image EXIF / Metadata / FileInfo without using an external DLL? Project: I'm building an app for personal use to rename, retag, and organize the apocalyptic quantity of images I host on my personal website. As I have been collecting funny pictures and such for several years, there is no real rhyme or reason to the file naming conventions. Ergo, Image0001.jpg needs to be renamed to a descriptive filename, and the Metadata fields need to be filled in. The desired process will take an existing jpg, gif, png, tiff or bmp and do the following: load image into

On the Bit Twiddling Hacks website the following algorithm is provided to round up an integer to the next power of two: unsigned int v; // compute the next highest power of 2 of 32-bit v v--; v |= v >> 1; v |= v >> 2; v |= v >> 4; v |= v >> 8; v |= v >> 16; v++; I would like to code a metaprogramming function that will compute the same operation: recursively (for compile-time execution) for any kind of integer (it should even work for possible awkward non-standard integers of any size like 15 bits, 65 bits...) and here is the form of the expected function: template <typename Type, // Something

At the moment, I'm using this method to check if a class has a method with a specific signature. After attending Walter E. Brown's metaprogramming CppCon2014 talk , I started wondering if void_t could be used in this particular situation to make the code cleaner and more readable. However I'm having trouble thinking in terms of void_t - so far I understand that void_t can help me determine at compile-time whether or not an expression is valid. Example: template< class, class = void > struct has_type_data_member : false_type { }; template< class T > struct has_type_data_member<T, void_t