I have to react to this. There is something called aliasing that prevent compilers to optimize, and passing builtins by const ref is generally NOT a good idea performance wise.
There is something called the const-forwarding type that resolves to value for built-ins and const refs for UDT that might be useful here.
Usually to solve this problem I simply use call_traits::param_type, is there any objection to this?
Finally, something that no one seems to be concerned about in this thread, is the cost of all these templates in terms of byte object code. In such a low-level header, you can expect all these templates to end up in every UoR in your libraries, linked together into an executable. Keeping positive_ and negative_ out of your template names is going to save that many bytes in your object. You may think its nothing. I've seen placeholders (_1 to _10) defined as static const Placeholder<N> take up to .5M for essentially nothing (it's an empty class!) We saved that .5MB by declaring them extern, as is done in Boost. So the rule is: keep it as simple and short as possible while remaining readable code.
OK I'll take a closer look at how the executable size changes with the different implementations, indeed it's a point I've forgotten a bit... Bruno