Re: [boost] [TypeErasure] Forward constructors and binded types

Subject: Re: [boost] [TypeErasure] Forward constructors and binded types
From: Vicente Botet (vicente.botet_at_[hidden])
Date: 2012-07-18 12:54:04

Vicente Botet wrote
> 
> 
> Steven Watanabe-4 wrote
>> 
>> AMDG
>> 
>> On 07/18/2012 06:57 AM, Larry Evans wrote:
>>> On 07/18/12 01:29, Vicente J. Botet Escriba wrote:
>>>> Hi,,
>>>>
>>>> In the example from the doc
>>> 
>>> http://steven_watanabe.users.sourceforge.net/type_erasure/libs/type_erasure/doc/html/boost_typeerasure/multi.html
>>> 
>>>>
>>>>     typedef mpl::vector<
>>>>         copy_constructible<_a>,
>>>>         copy_constructible<_b>,
>>>>         copy_constructible<_c>,
>>>>         constructible<_a(const _b&, const _c&)>
>>>>     > construct;
>>>>
>>>>     std::vector<double> vec;
>>>>     int i = 10;
>>>>     double d = 2.5;
>>>>     tuple&lt;construct, _a&amp;, _b, _c&gt; t(vec, i, d);
>>>>     any&lt;construct, _a&gt; v(get<1>(t), get<2>(t));
>>>>
>>>> I don't see which type is constructed and stored in v and how this type
>>>> is given. That is I don't see how _a is binded. Could you help me?
>>>>
>>> 
>>> I'd guess that a std::vector<double>&, more specifically the
>>> vec is stored as the _a& in the tuple&lt;construct, _&amp;a, _b, _c&gt;.
>>> Hmm...  Now I'm not sure anymore.  Maybe it's a new std::vector<double>
>>> that's stored and the std::vector<double> CTOR args are
>>> 10 and double.  IOW the equivalent of:
>>> 
>>>   std::vector<double> v_a(10,2.5)
>>> 
>>> is stored in v?
>>> 
>> 
>> Yes.
>> 
>>> Could the documentation on this be clarified a bit?
>>> 
>> 
>> What needs to be clarified?  This is the
>> only reasonable behavior:
>> The arguments obviously match
>> constructible<_a(const _b&, const _c&)> right?
>> Therefore this constructor is the one called.
>> _a was bound to std::vector<double>,
>> so this is the type created.
>> 
>> In Christ,
>> Steven Watanabe
>> 
> 
> My question is how the bind of _a to std::vector<double> if the t variable
> is not passed in the constructor of any? I'm sure I'm missing something
> evident.
> 
> 

Sorry I wanted to say, how the bind of _a to std::vector<double> *is know by
v* if the t variable is not passed in the constructor of any? 

Vicente

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