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istream_iterator

Started by godmodder Aug 22, 2008 at 3:34 PM 1 replies 750+ views

Original Post

Aug 22, 2008 at 3:34 PM

Hello, I want to read in a fixed amount of ASCII records from a file. I would like to know if I could do this using an STL algorithm. I know you can do the following: copy(istream_iterator(m_File), istream_iterator(), back_inserter(Book.m_Chapters)); What I would really like to do is something like this (doesn't work): copy(istream_iterator(m_File), istream_iterator(m_File) + NumOfChapters, back_inserter(Book.m_Chapters)); Is there a way to achieve this behavior or is there a better solution I don't know of? Thanks in advance, Jeroen

ToohrVyk

238

ToohrVyk

Aug 22, 2008 at 3:55 PM

No, this is not possible.

You can look into std::copy_n (which is an SGI extension) or reimplement it yourself:

template <typename In, typename Out>typename std::iterator_traits<In>::difference_type copy_n(In begin, In end, Out out,        typename std::iterator_traits<In>::difference_type count){  typename std::iterator_traits<In>::difference_type diff = 0;  while (diff != count && begin != end)   {    *out = *begin;    ++out;    ++begin;    ++count;  }  return diff;}

Mike nl

Aug 22, 2008 at 5:58 PM

Surely that should be ++diff; instead of ++count; ?

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