Method empty

deps/boost/boost/function/function_base.hpp:601–601

Determine if the function is empty (i.e., has no target). */

  /** Determine if the function is empty (i.e., has no target). */
  bool empty() const { return !vtable; }

  /** Retrieve the type of the stored function object, or type_id<void>()
      if this is empty. */