在您看来，打印到最优雅的方式是什么？ std::cout 运用 std::ostream_iterator 在C ++ 11中避免打印尾随分隔符？
我正在打印的对象具有双向迭代器，但不是随机访问迭代器。
std::list<double> x{1,2,3,4,5,6};
std::copy(x.begin(), std::prev(x.end()),
std::ostream_iterator<int>(std::cout, ",") );
if ( x.size() != 0 )
std::cout << *(--x.end()) << std::endl;
这是我的最爱之一，但它不使用 std::ostream_iterator：
#include <iterator>
#include <string>
#include <iosfwd>
template <class C>
auto
print(std::ostream& os, const C& c,
const std::string& delim = std::string(", "),
const std::string& open_brace = std::string("{"),
const std::string& close_brace = std::string("}")
) -> decltype(std::begin(c), std::end(c), os)
{
os << open_brace;
auto i = std::begin(c);
auto e = std::end(c);
if (i != e)
{
os << *i;
for (++i; i != e; ++i)
os << delim << *i;
}
os << close_brace;
return os;
}
#include <list>
#include <iostream>
int main()
{
std::list<double> x{1,2,3,4,5,6};
print(std::cout, x) << '\n';
}
{1, 2, 3, 4, 5, 6}
更新
奥利弗引发了我无法抗拒的挑战。 :-)
#include <iterator>
#include <string>
#include <iosfwd>
namespace my {
template <class C>
auto
print(std::ostream& os, const C& c,
const std::string& delim = std::string(", "),
const std::string& open_brace = std::string("{"),
const std::string& close_brace = std::string("}")
) -> decltype(std::begin(c), std::end(c), os);
template <class C,
typename std::enable_if
<
!std::is_same<C, std::string>::value,
bool>::type = false
>
inline
auto
operator<< (std::ostream& os, const C& c) -> decltype(print(os, c))
{
return print(os, c);
}
template <class C>
auto
print(std::ostream& os, const C& c,
const std::string& delim,
const std::string& open_brace,
const std::string& close_brace
) -> decltype(std::begin(c), std::end(c), os)
{
os << open_brace;
auto i = std::begin(c);
auto e = std::end(c);
if (i != e)
{
os << *i;
for (++i; i != e; ++i)
os << delim << *i;
}
os << close_brace;
return os;
}
}
#include <list>
#include <forward_list>
#include <iostream>
int main()
{
std::forward_list<std::list<double>> x{{}, {3, 2, 1}, {1,2,3,4,5,6}};
my::print(std::cout, x) << '\n';
}
{{}, {3, 2, 1}, {1, 2, 3, 4, 5, 6}}
它并不完美，但很有趣。 :-)可能有更好的方法来传播自定义分隔符和更忠实的括号。
只需将光标向后移动：
std::cout << "\b";
然后覆盖分隔符。
C ++ 14 - 遗憾的是需要输入/输出流：
#include <algorithm>
#include <iostream>
#include <iterator>
#include <sstream>
#include <list>
int main()
{
std::list<double> x{1,2,3,4,5,6};
std::stringstream sstr;
std::transform(x.begin(), x.end(), std::ostream_iterator<std::string>(sstr), [&](auto c){
return (sstr.rdbuf()->in_avail() ? "," : "") + std::to_string(c);
});
std::cout << sstr.str() << std::endl;
}
从C ++ 17开始 ostream_joiner 这将解决这个问题：
#include <algorithm>
#include <experimental/iterator>
#include <iostream>
#include <iterator>
int main()
{
int i[] = {1, 2, 3, 4, 5};
std::copy(std::begin(i),
std::end(i),
std::experimental::make_ostream_joiner(std::cout, ", "));
}