"I don't particularly understand what makes the second one more confusing than the first." To understand the first one, you only need to know the basic C++ con

"I don't particularly understand what makes the second one more confusing than the first." To understand the first one, you only need to know the basic C++ constructs. For the second one you need to know: * the meaning of the four positional arguments to accumulate() * the semantics of bind() * the semantics of boost's placeholders Even with some knowledge of the above, figuring out the nested binds takes a while.