Sent from my iPhone
Begin forwarded message: > From: Matthew Johnson <[email protected]> > Date: November 24, 2017 at 3:55:34 PM PST > To: Dave Abrahams <[email protected]> > Subject: Re: [swift-evolution] [Pre-pitch] Conditional default arguments > > You posted off-list. If that wasn’t intentional feel free to forward my > reply to the list. > > Sent from my iPad > >> On Nov 24, 2017, at 5:32 PM, Dave Abrahams <[email protected]> wrote: >> >> >>> On Nov 24, 2017, at 3:11 PM, Matthew Johnson via swift-evolution >>> <[email protected]> wrote: >>> >>> Adding language support for defining these more directly would eliminate a >>> lot of boilerplate >> >> I think I understand what you’re trying to do, but it’s not obvious to me >> that this pattern is common enough to warrant investing language design >> resources or the increased language complexity of a dedicated feature. > > It’s not obvious to me either. It’s not something I come across frequently, > but the overloads get painful pretty quickly in the cases where I do. > > When I initially added it to the manifesto I put it in the “maybe”section and > called it a “pre-pitch” for this reason. I posted on list because Doug had a > positive response to the idea. It may well be a case where solving it > directly at the language level isn’t appropriate. > > I don’t plan to push hard for it if the response is lukewarm. I’m primarily > interested in finding out what the response is at this point. :) > >> When you say “a lot of boilerplate,” how much do you mean? > > It’s a combinatoric explosion of overloads so it depends on the number of > conditionally defaulted arguments. > > The example I gave above is a simplification based on some code I have > written. This code already requires an overload set for other reasons. Each > of the base overloads requires a set providing emulated default arguments. > The total size of the set is uncomfortable. > >> Is this a pattern you’ve observed outside your own code? > > No, but I haven’t been actively looking for it. Part of the reason for > posting to the list is to seek feedback and see if others have had similar > cases arise. >
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