Is there any shortcut method to print 2D-array c++ - c++

Question

Is there any shortcut method in c++ to output 2d array(i.e. apart from for loop)?
Is there a special function in STL to output it.

Answer 1

Well, since you mentioned STL functions, you could use the std::for_each function with lambda functions to print the 2D array:
#include <iostream>
using namespace std;
int main(int argc, char *argv[]) {
int matrix[3][3] = { {1,2,3},{4,5,6},{7,8,9} };
auto elem_printer = [](int num) { std::cout << num << " "; };
auto row_printer = [&elem_printer](int (&row)[3]) {
std::for_each(std::begin(row),std::end(row),elem_printer);
std::cout << std::endl;
};
std::for_each(std::begin(matrix),std::end(matrix),row_printer);
}
However, this is exactly the same as two for loops, but uglier.

Answer 2

I have this template for streams, which hides away some of the ugliness, and you benefit from it being reusable and it handles multiple dimensions. There is no way to get away without doing the loops somewhere, of course:
template <class Stream, size_t depth>
class Pretty
{
Stream& s;
public:
Pretty(Stream& s): s(s) {}
template <size_t d1, typename T>
Stream& operator <<( T const (&v)[d1])const
{
const char* sep = "{";
for (auto& m : v)
{
s << sep << m;
sep = ", ";
}
s << "}";
return s;
}
template <size_t d1, typename T, size_t d2>
std::ostream& operator <<(T const (&v)[d1][d2])const
{
enum {DENT = 4};
std::string dent (DENT,' ');
std::string indent(depth*DENT,' ');
std::string sep = "{\n" + indent + dent;
for (auto& m : v)
{
s << sep; Pretty<Stream,depth+1>(s) << m;
sep = ",\n" + indent + dent;
}
s << "\n" << indent << "}";
return s;
}
};
class PrettyNext
{};
Pretty<std::ostream,0> operator << (std::ostream& s, const PrettyNext&)
{
return Pretty<std::ostream,0>(s);
}
And usage:
int i [][3][2] = { { {1,2}, {3,4}, {5,6} },{{0}}};
std::cout << "This is a test:\n" << PrettyNext() << i << std::endl;
Output is:
This is a test:
{
{
{1, 2},
{3, 4},
{5, 6}
},
{
{0, 0},
{0, 0},
{0, 0}
}
}
I have been fighting to get this to work directly on std::ostream, but there is a collision with the standard char* handling I can't quite resolve.