template<class eq, class vec, MsgKey Key>
tk::grm::action<check_vector_exists<eq, vec, Key>> struct

Check the existence of a vector (required for a block)

This functor can be used to check the existence of a user-specified vector, e.g., at the end of a diffeq ... end block, that is required for that block. If the vector does not exist, we error out.