hash_set in STL

[jian]

I am trying to use the hash_set, but cannot get it work. Here's my code:

 // file name: hash1.cpp 
#include <hash_set>
int main()
{
hash_set<int> h;
}
 
When I type:
g++ -c -I/usr/include/c++/4.0.3/ext hash1.cpp 
 
It shows lots of errors, anyone can tell me how to use hash_set correctly? Thanks a lot! (the following are the reported errors):
 
/usr/include/c++/4.0.3/ext/memory:74: error: ‘std::_Temporary_buffer’ has not been declared
/usr/include/c++/4.0.3/ext/memory:186: error: expected template-name before ‘<’ token
/usr/include/c++/4.0.3/ext/memory:186: error: expected `{' before ‘<’ token
/usr/include/c++/4.0.3/ext/memory:186: error: expected unqualified-id before ‘<’ token
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h: In destructor ‘std::_Temporary_buffer<_ForwardIterator, _Tp>::~_Temporary_buffer()’:
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h:129: error: ‘return_temporary_buffer’ is not a member of ‘std’
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h: In constructor ‘std::_Temporary_buffer<_ForwardIterator, _Tp>::_Temporary_buffer(_ForwardIterator, _ForwardIterator)’:
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h:152: error: ‘get_temporary_buffer’ was not declared in this scope
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h:153: error: expected primary-expression before ‘>’ token
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h:161: error: ‘return_temporary_buffer’ is not a member of ‘std’
hash1.cpp: In function ‘int main()’:
hash1.cpp:5: error: ‘hash_set’ was not declared in this scope
hash1.cpp:5: error: expected primary-expression before ‘int’
hash1.cpp:5: error: expected `;' before ‘int’
 

[Banfa]

I think you need to include

using namespace std
 

before main in order to use the STL. Also it appears that hash_set is not a mandatory member of the STL.

[jian]

Even if I add the "namespace", it still doesn't work. I know hash_set is not a member of the standard STL. But since I can find the declearation in my /usr/include/c++/4.0.3/ext/hash_set, and the library of STL is installed, I think there should be a way to use it, shouldn't it?

I think you need to include

using namespace std
 

before main in order to use the STL. Also it appears that hash_set is not a mandatory member of the STL.

[Banfa]

You are not declaing it correctly, you have too few items netween < and > in

    hash_set<int> h;
 

see http://www.sgi.com/tech/stl/hash_set.html for some help

[jian]

I actually copy paste the SGI example first, but the same problem occus. So I just made a minimal example to pasted here. So I'm sure this is not the problem. To convince you, let me paste another minimal example, truncated from SGI:

 #include <hash_set> 
using namespace std;
 
struct eqstr
{
bool operator()(const char* s1, const char* s2) const
{
return strcmp(s1, s2) == 0;
}
};
 
int main()
{
hash_set<const char*, hash<const char*>, eqstr> Set;
}
 
And the error messages are:
/usr/include/c++/4.0.3/ext/memory:74: error: ‘std::_Temporary_buffer’ has not been declared
/usr/include/c++/4.0.3/ext/memory:186: error: expected template-name before ‘<’ token
/usr/include/c++/4.0.3/ext/memory:186: error: expected `{' before ‘<’ token
/usr/include/c++/4.0.3/ext/memory:186: error: expected unqualified-id before ‘<’ token
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h: In destructor ‘std::_Temporary_buffer<_ForwardIterator, _Tp>::~_Temporary_buffer()’:
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h:129: error: ‘return_temporary_buffer’ is not a member of ‘std’
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h: In constructor ‘std::_Temporary_buffer<_ForwardIterator, _Tp>::_Temporary_buffer(_ForwardIterator, _ForwardIterator)’:
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h:152: error: ‘get_temporary_buffer’ was not declared in this scope
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h:153: error: expected primary-expression before ‘>’ token
/usr/lib/gcc/i486-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/stl_tempbuf.h:161: error: ‘return_temporary_buffer’ is not a member of ‘std’
hash1.cpp: In function ‘int main()’:
hash1.cpp:14: error: ‘hash_set’ was not declared in this scope
hash1.cpp:14: error: expected primary-expression before ‘const’
hash1.cpp:14: error: expected `;' before ‘const’
 

[Hai Jin]

Hi:

I ran into the same thing as you. And I found in MS VS 2005, you need to do the following

using namespace stdext;

See below for what I copied from VS 2005 online help:

Members of the <hash_map> and <hash_set> header files are not currently part of the ISO C++ standard. Therefore, these types and members have been moved from the std namespace to namespace stdext, to remain conformant with the C++ standard.

When compiling with /Ze, which is the default, the compiler will warn on the use of std for members of the <hash_map> and <hash_set> header files. To disable the warning, use the warning pragma.

To have the compiler generate an error for the use of std for members of the <hash_map> and <hash_set> header files with /Ze, add the following directive before #include'ing any Standard C++ Library header files.