Comments on: Implementing Default Parameters That Depend on Other Parameters in C++

By: Jonathan Boccara

Jonathan Boccara — Mon, 20 Aug 2018 11:31:00 +0000

Thanks all for your feedback!!

By: Vincent Zalzal

Vincent Zalzal — Sat, 18 Aug 2018 05:37:00 +0000

I am sorry, but I have to agree with the other commenters. At this point, I think this is more confusing than helpful to the person reading the code. Also, in the previous post, your solution had the advantage to be fully specified in the function declaration, which is not the case here. Indeed, the caller has no way to know which parameters will be passed to the function without looking at the function definition (x+y? x+x? 2*x + y?). So, this is no better than using an optional directly as parameter, in my opinion.

By: Chet Skolos

Chet Skolos — Sat, 18 Aug 2018 02:02:00 +0000

In reply to David Álvarez Fernández. Inline overload in the header will accomplish the same thing. I could not agree more.

By: Aksel Huff

Aksel Huff — Sat, 18 Aug 2018 00:59:00 +0000

Seems like a code design problem to me. Why you want a function to be dependent on other arguments but also able to be set by the caller? Surely these should be separate overloaded constructors as the purpose of each constructor is different. Or maybe use a factory?

By: jft

jft — Fri, 17 Aug 2018 18:28:00 +0000

The underlying issue(s) are defects in the c++ language spec itself. IMO these should be addressed in the language standard rather than with ‘work arounds’ with convoluted templated code which just increases the code complexity. Personally, I agree with David that my preferred implementation for this would be via function overload.

By: David Álvarez Fernández

David Álvarez Fernández — Fri, 17 Aug 2018 06:28:00 +0000

IMHO the code gets too messy, and (a bit) difficult to follow. Wouldn’t be cleaner just to overload and compose the z argument in the 2 argument version of the function? I know that if you have too many variants it can also get messy, but if that is the case maybe it is a good moment to refactor.