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Re: Request för std::vector and possibly others: minimal initalization

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On Monday, March 19, 2012 11:35:35 PM UTC-7, henrikv wrote:
>  Hello group!
>
>  When writing parallel code, I often allocate a vector for results. I
>  allocate the complete vector with a single resize. What I'd like to do
>  is to tell the resize not to initialize the content, since this will
>  be overwritten anyway. I'd figure something like:
>
>  struct no_init {} g_no_int;
>
>  struct Dummy
>  {
>   Dummy(int a_=0) : a(a_) {}
>   Dummy(const no_init&) {} // Without a v-table, this shouldn't need
>  to
>  touch any part of the created object?
>
>   int a;
>  };
>
>  void foo()
>  {
>   std::vector<Dummy>  dummies;
>   dummies.resize(1000, g_no_int);
>   // ...
>  }
>
>  Proposal: add a method to std::vector that allows resize with a
>  different constructor than default or copy
>  constructor:
>
>                 template<typename T2>
>                 void resize_construct_using_translation(size_t n, const T2&t2);
>
>  Any thoughts on this?
>
>  Best regards,
>  Henrik Vallgren
>

This looks more like an improper use of `std::vector` than anything that should be added to the specification.

All you need to do is use `std::vector::reserve` to allocate as much space as you plan to use. Then use `emplace_back` to construct each addition to the `vector` in-place.


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Request för std::vector and possibly others: minimal initalization henrikv <henrik.vallgren@stream-space.com> - 2012-03-19 23:35 -0700
  Re: Request för std::vector and possibly others: minimal initalization Francis Glassborow<francis.glassborow@btinternet.com> - 2012-03-21 11:35 -0700
    Re: Request för std::vector and possibly others: minimal initalization henrikv<henrik.vallgren@stream-space.com> - 2012-03-23 17:09 -0700
      Re: Request för std::vector and possibly others: minimal initalization Daniel Krügler <daniel.kruegler@googlemail.com> - 2012-03-24 19:25 -0700
      Re: Request för std::vector and possibly others: minimal initalization Francis Glassborow <francis.glassborow@btinternet.com> - 2012-03-24 19:28 -0700
  Re: Request för std::vector and possibly others: minimal initalization Jason McKesson<jmckesson@gmail.com> - 2012-03-21 11:35 -0700
    Re: Request för std::vector and possibly others: minimal initalization henrikv<henrik.vallgren@stream-space.com> - 2012-03-23 17:10 -0700
      Re: Request för std::vector and possibly others: minimal initalization Jason McKesson<jmckesson@gmail.com> - 2012-03-24 17:55 -0700
      Re: Request for std::vector and possibly others: mi brangdon@cix.compulink.co.uk (Dave Harris) - 2012-03-24 19:24 -0700
      Re: Re: Request för std::vector and possibly others: minimal initalization jgk@panix.com (Joe keane) - 2012-03-27 12:10 -0700
    Re: Request för std::vector and possibly others: minimal initalization Kevin McCarty<kmccarty@gmail.com> - 2012-03-23 17:11 -0700
      Re: Request för std::vector and possibly others:   minimal initalization Miles Bader<miles@gnu.org> - 2012-03-24 17:55 -0700
        Re: Request för std::vector and possibly others: minimal initalization henrikv <henrik.vallgren@stream-space.com> - 2012-03-25 23:14 -0700
      Re: Request för std::vector and possibly others: minimal initalization Jason McKesson <jmckesson@gmail.com> - 2012-03-24 19:27 -0700
      Re: Request för std::vector and possibly others: minimal initalization Pedro Lamarão<pedro.lamarao@gmail.com> - 2012-03-29 12:28 -0700
        Re: Request för std::vector and possibly others: minimal initalization Daniel Krügler <daniel.kruegler@googlemail.com> - 2012-03-29 13:17 -0700

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