Re: [boost] [variant] awkward recursion

Subject: Re: [boost] [variant] awkward recursion
From: Dave Abrahams (dave_at_[hidden])
Date: 2012-10-29 16:43:35

on Mon Oct 29 2012, Dave Abrahams <dave-AT-boostpro.com> wrote:

> I've been playing around with variant a bit and decided to try to build
> a data structure for storing json.  I came up with several different
> approaches but none are super-satisfying.  I'd like some feedback.  (If
> you need a refresher on what's in json, the front page of
> http://json.org tells all).

I got *some* answers to my questions by experimentation:  https://gist.github.com/3976374

Output:

  size of objects: 48, 48, 48
  size of arrays: 24, 24, 24
  size of variants: 56, 16, 16

What I learned is that using either recursive_wrapper or
recursive_variant_ *does* seem to introduce an indirection even if one
isn't needed.  I also learned that 8 bytes are used for a discriminant
on my x64 system, which I'll grudgingly admit might be the best we can
do.  But only grudgingly.

Comments on other questions in that message are still appreciated.
-- 
Dave Abrahams
BoostPro Computing                  Software Development        Training
http://www.boostpro.com             Clang/LLVM/EDG Compilers  C++  Boost