[swift-evolution] [Pitch] Add the DefaultConstructible protocol to the standard library

Dave Abrahams dave at boostpro.com
Mon Dec 26 11:18:00 CST 2016

on Mon Dec 26 2016, Xiaodi Wu <xiaodi.wu-AT-gmail.com> wrote:

> The question still remains unanswered, what generic algorithms are enabled
> by having such a protocol? 

That is really the key question, and until it can be answered
satisfactorily, I will continue to be -1 on the idea.  My sense of the
arguments for the protocol is that they amount to, “please, it's
obvious; to do anything else would be absurd.”  That sort of response
tends to make me even more suspicious of any idea.  There are lots of
things we've done in Swift that looked absurd to someone but turned out
to be exactly right.

Here is a bit of truly friendly advice for those proposing
DefaultConstructible.  If you really believe in this idea and you want
the proposal to be a succeess, you should try to approach the problem
this way:

1. Understand the principle behind what Wu and I are saying.
2. Set aside what appears to be your base assumption that the protocol
   makes sense and pretend you need to be convinced.
3. Sincerely answer the question Wu is asking in such a way that it
   would convince the “unconvinced you.”


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