Re: forward declaring std::vector. Works, but is it legal and standard compliant?

On Oct 28, 7:22 am, Jerry Coffin <jcof...@taeus.com> wrote:


Which means that ideally the standard should provide these forward
declarations in a header, I guess? Or is there a client solution to
this problem that is satisfactory? Or is the potential benefits from
not having to include the header deemed insignificant?

A simple typedef cannot be forward-declared, but obviously you could
encapsulate the std container inside a user type:

// Client header

struct std_vector;

struct Foo
{
  void bar (std_vector const& v);
};

// Client implementation

#include <vector>
#include <iterator>
#include <algorithm>
#include <iostream>

using namespace std;

struct std_vector
{
  vector <int> v;
};

void Foo::bar (std_vector const& v)
{
  copy (v.v.begin (), v.v.end (),
    ostream_iterator <int, char> (cout, " "));
}

int main()
{
  // By exploiting initialization lists
  // we avoid duplicating constructors.

  int k [] = {3, 4};
  std_vector v = {vector <int> (k, k + 2)};

  Foo foo;
  foo.bar (v);
}

Regards,
Vidar Hasfjord

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