copy_n from GNU C++ Library

[flylehe]

Hi,
I am using copy_n from GNU C++ Library under Ubuntu 8.10. My code is like this:


#include <ext/algorithm>
using namespace std;

void myfun(char * flags ) {
char * flags_new = new char[3];
copy_n(flags, 3, flags_new);// both copy_n and copy would give not in this scope error.
delete [] flags_new;
}

int main()
{
char flags[3]={'a','b','c'};
myfun(flags );
return 0;
}

I got error : "‘copy_n’ was not declared in this scope".
I look up for copy_n in GNU C++ standard library document and find "ext/algorithm" to include. I was wondring what is the problem and how to fix it? Thanks!

[dwhitney67]

I don't quite understand what you are seeking, nor why you are attempting to use a function that is not covered by the C++ standard, but instead a GNU extension. Your code may not be portable to another system. But if that is what you want, I think the only issue you need to be aware of is that copy_n() is not part of the std namespace; it is part of the __gnu_cxx namespace.



#include <ext/algorithm> // this header also includes <algorithm>
#include <iostream>

void dispChar(const char ch)
{
std::cout << ch << " ";
}

void myfun(const char* flags)
{
char* flags_new = new char[3];

__gnu_cxx::copy_n(flags, 3, flags_new);

std::for_each(flags_new, flags_new+3, dispChar);
std::cout << std::endl;

delete [] flags_new;
}

int main()
{
char flags[3] = {'a','b','c'};

std::for_each(flags, flags+3, dispChar);
std::cout << std::endl;

myfun(flags);
}