Re: [boost] Heterogeneous Container Library (HCL) Feedback and Testing

Subject: Re: [boost] Heterogeneous Container Library (HCL) Feedback and Testing
From: Andrzej Krzemienski (akrzemi1_at_[hidden])
Date: 2015-06-05 05:20:04

2015-06-04 0:48 GMT+02:00 Evgeny Panasyuk <evgeny.panasyuk_at_[hidden]>:

> 03.06.2015 23:42, Andrzej Krzemienski:
>
>> Could you provide some sketch of a real life scenario? The examples show
>> how I can use it, but I fail to imagine why I would need it. You mentioned
>> storing the results of various DB queries, how would you make use of data
>> stored in such way?
>>
>
> For example, It can be used as fast drop-in replacement for
> std::vector<boost::variant<Types...>> in case when order of elements
> (across different types) is not important.
> For instance CAD application may want to process all objects, like draw
> all of them or apply some filter or serialize. There is no need to pay cost
> of dynamic dispatch on each element.
>

A replacement for  std::vector<boost::variant<Types...>> in order to get
performance -- agreed. Not a "drop-in" one though, I think, because If I
change the type, I need to go and change every place that is using it,
right? And if I am forced to restructure my code, why would I not just use:

struct variantvector
{
 std::vector<T1> t1;
 std::vector<T2> t2;
};

?

In other words, I am not questioning the idea of the optimization, but the
usefulness of the library. My understanding (as of now) is that compared to
a hand-crafted solution it offers (1) different names for the
sub-containers, and (2) a function that returns the sum of sizes of
individual containers.

Regards,
&rzej

>
> By the way,
> https://akrzemi1.wordpress.com/2013/12/11/type-erasure-part-iii/#comment-1752
>
> Best Regards,
> Evgeny Panasyuk
>
>
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