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

Subject: Re: [boost] [TypeErasure] Forward constructors and binded types
From: Larry Evans (cppljevans_at_[hidden])
Date: 2012-07-18 16:08:33

On 07/18/12 13:43, Vicente Botet wrote:
> 
> Steven Watanabe-4 wrote
>>
>> AMDG
>>
>> On 07/18/2012 10:47 AM, Vicente Botet wrote:
>>>
>>> Is the following correct?
>>>
>>>      class X {
>>>      public:
>>>        X(int, double);
>>>      };
>>>
>>>     std::vector<double> vec;
>>>     int i = 10;   
>>>     double d = 2.5;
>>>     X x;
>>>
>>>     tuple&lt;construct, _a&amp;amp;, _b, _c&gt; t1(vec, i, d);
>>>     tuple&lt;construct, _a&amp;amp;, _b, _c&gt; t2(x, i, d);
>>>     any&lt;construct, _a&gt; v1(get<1>(t1), get<2>(t1));
>>>     any&lt;construct, _a&gt; v2(get<1>(t2), get<2>(t2));
>>>
>>> If yes, how v1 is bound to vec and v2 to x?
>>>
>>
>> It isn't.  v1 stores a std::vector<double> which
>> is constructed in place and is not related to vec
>> in any way.
>>
>> v2 again hold a separate object of type X,
>> which is created using X(int, double).
>>
> 
> Well, I think I have understood how this can work.
> 
> get<1>(t1) returns an any that has a binding std::vector<double>,int,double
> and is this binding that allows to associate _a to std::vector<double>.
> 
> I 'd appreciate if the documentation clarifies what these bindings are, how
> they are built built and used.
> 
+1

Before Vicente mentioned the binding thing, I thought:

  get<1>(t1)

would return an any which was bound to an int, and:

  get<2>(t1)

would return an any which was bound to a double,
but now, if Vicente is correct, the get's return
an any that has the complete construct bindings.

Thanks Vicente.

-regards,
Larry