tmp-lib

Template magic library

Random tricks

You may find these useful when you have no idea how to do that template magic.

• Union. Nowadays unions have no other use case than adding workaround possibilities to the standard. Hint: a reinterpret_cast is forbidden at compile time via unions as well, but members' address may be taken. Example: offset_of.

• Fake a method by a member with a function call operator. Example: Property

• You can enumerate an argument pack's types by their indices as well. Example: variadic_insert

• Each lambda has a unique type. If you have two template stuff that should generate different template instances, extend it with a dummy lambda template parameter. Example: to_fptr.

• Have a lambda (member) instead of a regular function, as they have special skills. They might be stored in variables even if templated. Example: overload

• If you are struggling with passing stuff at compile time, create a carrier struct with regular members initialized at the declaration, and pass that as a typename. You may default construct them anywhere and their members will instantly contain your value. You can hide the additional boilerplate with a macro. Example: overload

• Everything fits into a void* in a type safe manner: functions, methods, arguments, etc. Create an aggregate struct with any data, and the first member should be a function pointer that knows everything about the latter members, and unpacks the original void*. When you get that void* data, calling (*static_cast<unpacker*>(data))(data) will do the job.

• Create a dummy function with no definitions to substitute arguments manually. Use their return value in a decltype, which is typically a (member) function pointer.

• Separate template parameters: put the function into a standalone struct with a portion of the original parameters. Mostly useful if you need to have two argument packs in a single function.