Re: [boost] [variant] awkward recursion

Subject: Re: [boost] [variant] awkward recursion
From: Dave Abrahams (dave_at_[hidden])
Date: 2012-10-29 17:15:39

on Mon Oct 29 2012, Agustín K-ballo Bergé <kaballo86-AT-hotmail.com> wrote:

> On 29/10/2012 04:29 p.m., Dave Abrahams wrote:
>> In the abstract, json looks like:
>>
>>    struct null {};
>>    typedef std::map<std::string, value> object;
>>    typedef std::vector<value> array;
>>
>>    typedef variant<
>>       null, std::string, double, object, array, bool
>>    > value;
>
> Keep in mind that instantiating a standard container with an
> incomplete type will yield undefined behavior, and that `variant` has
> to instantiate both `object` and `array` to know their size. In my own
> JSON attempt I have used Boost.Containers, which do guarantee defined
> behavior when instantiated with incomplete types.

I haven't instantiated anything at that point in the code, though.  By
the time the containers are instantiated, the types are complete. :-)

-- 
Dave Abrahams
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