Re: cout << vector<string>
James Kanze wrote:
On Nov 7, 1:32 pm, Jeff Schwab <j...@schwabcenter.com> wrote:
Pete Becker wrote:
On 2008-11-07 06:03:15 -0500, Maxim Yegorushkin
<maxim.yegorush...@gmail.com> said:
The example probably assumes there is an overloaded operator<<() for
std::ostream and std::vector<>, something like this:
namespace std {
template<class A1, class A2>
ostream& operator<<(ostream& s, vector<A1, A2> const& vec)
Which has undefined behavior. You can only add template specializations
to namespace std when they depend on user-defined types.
The correct alternative, AIUI:
#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>
template<typename T>
std::ostream& operator<<(std::ostream& out, std::vector<T> const& v) {
if (!v.empty()) {
typedef std::ostream_iterator<T> out_iter;
copy(v.begin(), v.end() - 1, out_iter( out, " " ));
out << v.back();
}
return out;
}
int main() {
int const ints[] = { 1, 2, 3, 4 };
std::cout << std::vector<int>( ints, ints + 4 ) << '\n';
}
Correct in what sense? It's OK for simple test, like this, but
it's certainly not something you'd allow in production code.
Correct in the sense that it implements the OP's intent, and is allowed
by the standard. As far as using it in production code... Ad hoc
output of this sort only really comes up for debugging purposes. If you
don't even think it's OK for debug, I'd love to know your suggested
alternative.