Re: [Cppcms-users] cppcms::json::value desing question

[Artyom <art...@ya...>]

> Hello Artyom
>
>I think that boost::variant type fits exactly as base class for
> cppcms::json::value.
>
> I think that one pro of this approach is that boost::variant interface
> is more familiar and has good visitor interface.
> 
> You think about that?
> 
> This break your ABI requirerements?

Exactly. See http://cppcms.sourceforge.net/wikipp/en/page/cppcms_1x_coding_standards#abi_boost

I can't use Boost libraries in CppCMS interfaces for very simple
reason: they ABI can be easily broken even with simple define addition
in headers. For example boost::shared_ptr changes its strucutres layout
with special define.

So I can't use Boost in iterfaces. 2nd issue is that AFAIK boost::variant
does not have virtual descructor so deriving from it is bad idea.

However I use exactly boost::variant in implementation of cppcms::json.

> Another question. You define json::object as std::map, which it has
> O(log n) complexity for access
>
> Why you not use boost::unordered_map which it has O(n) complexity?

Same reason as above, untill std::unordered_map would be availible
in major compilers I would use std::map.

Also, please note, that for relatively small maps, std::map would be 
even faster (and this is the case in most json objects).

Artyom

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