Re: constructing vector<POD> that is member of a class from an input stream (file)

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 18 Nov 2009 00:53:58 -0800 (PST)

Message-ID:

<a6c22da1-5a68-4651-8490-6b5dc8cf1610@p35g2000yqh.googlegroups.com>

On Nov 17, 10:20 pm, red floyd <redfl...@gmail.com> wrote:

On Nov 17, 12:02 pm, "Hicham Mouline" <hic...@mouline.org> wrote:

I have a text file with this format:

floating11 floating12 floating13 floating14
floating21 floating22 floating23 floating24
...
floatingN1 floatingN2 floatingN3 floatingN4

I have a simple struct

struct F {
  double d1;
  double d2;
  double d3;
  double d4;
};

and a
std::vector<F> v;

then a class C which adds intelligence to the processing of
the vector of Fs.
class C {
  C(const std::istream& input);
private:
  std::vector<F> v_;
};

I wish to construct an instance of C from a file.
I thought to use the iterator form of vector<F>'s ctor.

Do I write an iterator class that when dereferenced, points
to an instance of F, so that I can do

C::C(const std::istream& input)
: v_( begin, end )
{}

Was there a stream_iterator in std?

I understand there is some elegant form to fill up a vector
as;
std::copy( ? , ? , v_.back_inserter() );

Is there a similar form for vector construction?

Use std::istream_iterator<>.
You need to define operator<< for F.

That would be operator>>, of course, for input. And the two
iterator constructor for vector (paying attention that you
actually do define a vector, and not just declare a function
that returns one---you'll typically need an extra pair of
parentheses somewhere).

--
James Kanze