GCC中使用hash_map
2010-09-07 17:44
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GCC中使用hash_map
2009-04-01 21:34
最近学习STL,hash_map就是利用hash表实现的一个map,在查找是具有更快的效率,前提是你使用了适当的hash函数。hash_map不是STL中的一部分,但大多数C/c++的编译器都提供了这个容器。GCC也不例外,我在winds下使用的IDE是code blocks,它使用的编译器就是GCC。因为hash_map不是STL中的一部分,所以使用起来也不是很异样。下面的是我搜索到的一些资料:
Then you have realized that the code above does not compile. That's because on GCC, hash_map is not regarded as a standard container, but rather as a extension included in the
__gnu_cxx namespace. In order to use hash_map and other extended containers with a minimum impact in your code (which is very important if it's intended to be cross-platform),
you can use the following solution:
Hope that helps.
----------------------------------------------------------------------------------------------------------------------------------
【2】
http://www.velocityreviews.com/forums/t280027-why-wont-this-hashmap-compile.html
Hi,
I'm trying to use hash_map (gcc 3.2.2) with a std::string as the key. It
will compile if I use <map> but I get a bunch of template compile errors
when I change it to hash_map. Any suggestions? My program and the errors
are below...
#include <ext/hash_map>
#include <string>
using namespace std;
__gnu_cxx::hash_map<string, int> storage;
int main()
{
pair<string, int> item("blah", 1);
storage.insert(item);
}
When compiled I get the following:
g++ hm.cpp -o hm
/usr/include/c++/3.2.2/ext/stl_hashtable.h: In member function `size_t
__gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey,
_Alloc>::_M_bkt_num_key(const _Key&, unsigned int) const [with _Val =
std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const std::string, int>, _Key = std::string, _HashFcn =
__gnu_cxx::hash<std::string>, _ExtractKey = std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const
std::string, int> >, _EqualKey = std::equal_to<std::string>, _Alloc =
std::allocator<int>]':
/usr/include/c++/3.2.2/ext/stl_hashtable.h:522: instantiated from `size_t
__gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey,
_Alloc>::_M_bkt_num(const _Val&, unsigned int) const [with _Val =
std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const std::string, int>, _Key = std::string, _HashFcn =
__gnu_cxx::hash<std::string>, _ExtractKey = std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const
std::string, int> >, _EqualKey = std::equal_to<std::string>, _Alloc =
std::allocator<int>]'
/usr/include/c++/3.2.2/ext/stl_hashtable.h:887: instantiated from `void
__gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey,
_Alloc>::resize(unsigned int) [with _Val = std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const std::string,
int>, _Key = std::string, _HashFcn = __gnu_cxx::hash<std::string>,
_ExtractKey = std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const std::string, int> >, _EqualKey
= std::equal_to<std::string>, _Alloc = std::allocator<int>]'
/usr/include/c++/3.2.2/ext/stl_hashtable.h:381: instantiated from
`std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<__gnu_cxx::_Hashtable_iterator<_Val, _Key, _HashFcn, _ExtractKey,
_EqualKey, _Alloc>, bool> __gnu_cxx::hashtable<_Val, _Key, _HashFcn,
_ExtractKey, _EqualKey, _Alloc>::insert_unique(const _Val&) [with _Val =
std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const std::string, int>, _Key = std::string, _HashFcn =
__gnu_cxx::hash<std::string>, _ExtractKey = std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const
std::string, int> >, _EqualKey = std::equal_to<std::string>, _Alloc =
std::allocator<int>]'
/usr/include/c++/3.2.2/ext/hash_map:171: instantiated from
`std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<__gnu_cxx::hashtable<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const
_Key, _Tp>, _Key, _HashFcn,
std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const _Key, _Tp> >, _EqualKey, _Alloc>::iterator,
bool> __gnu_cxx::hash_map<_Key, _Tp, _HashFcn, _EqualKey,
_Alloc>::insert(__gnu_cxx::hashtable<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<con st _Key, _Tp>, _Key,
_HashFcn, std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const _Key, _Tp> >, _EqualKey,
_Alloc>::value_type&) [with _Key = std::string, _Tp = int, _HashFcn =
__gnu_cxx::hash<std::string>, _EqualKey = std::equal_to<std::string>, _Alloc
= std::allocator<int>]'
hm.cpp:14: instantiated from here
/usr/include/c++/3.2.2/ext/stl_hashtable.h:517: no match for call to `(const
__gnu_cxx::hash<std::string>) (const std::basic_string<char,
std::char_traits<char>, std::allocator<char> >&)'
make: *** [hm] Error 1
Mark
-----------------------------------------------------------------------------------------------------------------------------------
【3】
To: Matthew Sundling <sundlm at cs dot wisc dot edu>
Cc: libstdc++ at gcc dot gnu dot org
Date: Mon, 08 Apr 2002 23:42:45 +0200
Subject: Re: gcc-3.0.2 + hash_map<string,int> compilation problems
Organization: Noname4us
References: <Pine.GSO.4.21.0204081557530.14231-100000@nova5.cs.wisc.edu>
2009-04-01 21:34
最近学习STL,hash_map就是利用hash表实现的一个map,在查找是具有更快的效率,前提是你使用了适当的hash函数。hash_map不是STL中的一部分,但大多数C/c++的编译器都提供了这个容器。GCC也不例外,我在winds下使用的IDE是code blocks,它使用的编译器就是GCC。因为hash_map不是STL中的一部分,所以使用起来也不是很异样。下面的是我搜索到的一些资料:
【1】
http://zitronensaft.blogspot.com/2008/02/using-hashmap-on-gcc.html
Using hash_map on GCC
If you have tried to use some STL containers with GCC, such as hash_map:// error: hash_map: No such file or directory #include <hash_map> int main () { // error: ‘hash_map’ is not a member of ‘std’ std:: hash_map< int , int > hm; return 0 ; }
Then you have realized that the code above does not compile. That's because on GCC, hash_map is not regarded as a standard container, but rather as a extension included in the
__gnu_cxx namespace. In order to use hash_map and other extended containers with a minimum impact in your code (which is very important if it's intended to be cross-platform),
you can use the following solution:
#ifdef __GNUC__ #include <ext/hash_map> #else #include <hash_map> #endif namespace std { using namespace __gnu_cxx ; } int main () { std:: hash_map< int , int > hm; return 0 ; }
Hope that helps.
----------------------------------------------------------------------------------------------------------------------------------
【2】
http://www.velocityreviews.com/forums/t280027-why-wont-this-hashmap-compile.html
Hi,
I'm trying to use hash_map (gcc 3.2.2) with a std::string as the key. It
will compile if I use <map> but I get a bunch of template compile errors
when I change it to hash_map. Any suggestions? My program and the errors
are below...
#include <ext/hash_map>
#include <string>
using namespace std;
__gnu_cxx::hash_map<string, int> storage;
int main()
{
pair<string, int> item("blah", 1);
storage.insert(item);
}
When compiled I get the following:
g++ hm.cpp -o hm
/usr/include/c++/3.2.2/ext/stl_hashtable.h: In member function `size_t
__gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey,
_Alloc>::_M_bkt_num_key(const _Key&, unsigned int) const [with _Val =
std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const std::string, int>, _Key = std::string, _HashFcn =
__gnu_cxx::hash<std::string>, _ExtractKey = std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const
std::string, int> >, _EqualKey = std::equal_to<std::string>, _Alloc =
std::allocator<int>]':
/usr/include/c++/3.2.2/ext/stl_hashtable.h:522: instantiated from `size_t
__gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey,
_Alloc>::_M_bkt_num(const _Val&, unsigned int) const [with _Val =
std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const std::string, int>, _Key = std::string, _HashFcn =
__gnu_cxx::hash<std::string>, _ExtractKey = std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const
std::string, int> >, _EqualKey = std::equal_to<std::string>, _Alloc =
std::allocator<int>]'
/usr/include/c++/3.2.2/ext/stl_hashtable.h:887: instantiated from `void
__gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey,
_Alloc>::resize(unsigned int) [with _Val = std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const std::string,
int>, _Key = std::string, _HashFcn = __gnu_cxx::hash<std::string>,
_ExtractKey = std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const std::string, int> >, _EqualKey
= std::equal_to<std::string>, _Alloc = std::allocator<int>]'
/usr/include/c++/3.2.2/ext/stl_hashtable.h:381: instantiated from
`std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<__gnu_cxx::_Hashtable_iterator<_Val, _Key, _HashFcn, _ExtractKey,
_EqualKey, _Alloc>, bool> __gnu_cxx::hashtable<_Val, _Key, _HashFcn,
_ExtractKey, _EqualKey, _Alloc>::insert_unique(const _Val&) [with _Val =
std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const std::string, int>, _Key = std::string, _HashFcn =
__gnu_cxx::hash<std::string>, _ExtractKey = std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const
std::string, int> >, _EqualKey = std::equal_to<std::string>, _Alloc =
std::allocator<int>]'
/usr/include/c++/3.2.2/ext/hash_map:171: instantiated from
`std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<__gnu_cxx::hashtable<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const
_Key, _Tp>, _Key, _HashFcn,
std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const _Key, _Tp> >, _EqualKey, _Alloc>::iterator,
bool> __gnu_cxx::hash_map<_Key, _Tp, _HashFcn, _EqualKey,
_Alloc>::insert(__gnu_cxx::hashtable<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<con st _Key, _Tp>, _Key,
_HashFcn, std::_Select1st<std:
![](http://www.velocityreviews.com/forums/images/smilies/icon_razz.gif)
air<const _Key, _Tp> >, _EqualKey,
_Alloc>::value_type&) [with _Key = std::string, _Tp = int, _HashFcn =
__gnu_cxx::hash<std::string>, _EqualKey = std::equal_to<std::string>, _Alloc
= std::allocator<int>]'
hm.cpp:14: instantiated from here
/usr/include/c++/3.2.2/ext/stl_hashtable.h:517: no match for call to `(const
__gnu_cxx::hash<std::string>) (const std::basic_string<char,
std::char_traits<char>, std::allocator<char> >&)'
make: *** [hm] Error 1
Mark
-----------------------------------------------------------------------------------------------------------------------------------
【3】
Re: gcc-3.0.2 + hash_map<string,int> compilation problems
From: Stefan Olsson <stefan at noname4us dot com>To: Matthew Sundling <sundlm at cs dot wisc dot edu>
Cc: libstdc++ at gcc dot gnu dot org
Date: Mon, 08 Apr 2002 23:42:45 +0200
Subject: Re: gcc-3.0.2 + hash_map<string,int> compilation problems
Organization: Noname4us
References: <Pine.GSO.4.21.0204081557530.14231-100000@nova5.cs.wisc.edu>
Hi! I have had the same issue and solved it by declaring: #include <string> #include <ext/hash_map> namespace __gnu_cxx { template<> struct hash< std::string > { size_t operator()( const std::string& x ) const { return hash< const char* >()( x.c_str() ); } }; } I guess that the reason for not having this declared in the std::string is that the hash* are extensions to the standard. Maybe something like the above could be added into the codebase somewhere else? Hope that helps! /Stefan Matthew Sundling wrote: >I have been trying to compile an extremely simple program that >uses a hash_map<string, int>. I can't quit figure out what the >errors are telling to supply to the STL container to satisfy it. > >Thanks for any insight you might have: > >[---------------------------------------------------------------] >My program: > >#include <iostream> >#include <string> >#include <ext/hash_map> > >int main () { > std::hash_map<std::string, int > str_hash; > str_hash["text"] = 1; > std::cout << str_hash["test"] << std::endl; > return 0; >} > > >[---------------------------------------------------------------] >My gcc output: > >/s/unsup/include/g++-v3/ext/stl_hashtable.h: In member function >`size_t std::hashtable<_Val, _Key, _HashFcn, _ExtractKey, >_EqualKey, _Alloc>::_M_bkt_num_key(const _Key&, unsigned int) const >[with _Val = std::pair<const std::string, int>, >_Key = std::string, >_HashFcn = std::hash<std::string>, >_ExtractKey = std::_Select1st<std::pair<const std::string, int> > >>, >> >_EqualKey = std::equal_to<std::string>, >_Alloc = std::allocator<int>]': > >/s/unsup/include/g++-v3/ext/stl_hashtable.h:512: instantiated >from `size_t std::hashtable<_Val, _Key, _HashFcn, _ExtractKey, >_EqualKey, _Alloc>::_M_bkt_num(const _Val&, unsigned int) const >[with _Val = std::pair<const std::string, int>, >_Key = std::string, _HashFcn = std::hash<std::string>, >_ExtractKey = std::_Select1st<std::pair<const std::string, int> > >>, >> >_EqualKey = std::equal_to<std::string>, >_Alloc = std::allocator<int>]' > >/s/unsup/include/g++-v3/ext/stl_hashtable.h:856: instantiated >from `void std::hashtable<_Val, _Key, _HashFcn, _ExtractKey, >_EqualKey, _Alloc>::resize(unsigned int) >[with _Val = std::pair<const std::string, int>, >_Key = std::string, >_HashFcn = std::hash<std::string>, >_ExtractKey = std::_Select1st<std::pair<const std::string, int> > >>, >> >_EqualKey = std::equal_to<std::string>, >_Alloc = std::allocator<int>]' > >/s/unsup/include/g++-v3/ext/stl_hashtable.h:669: instantiated >from `_Val& std::hashtable<_Val, _Key, _HashFcn, _ExtractKey, >_EqualKey, _Alloc>::find_or_insert(const _Val&) >[with _Val = std::pair<const std::string, int>, >_Key = std::string, >_HashFcn = std::hash<std::string>, >_ExtractKey = std::_Select1st<std::pair<const std::string, int> > >>, >> >_EqualKey = std::equal_to<std::string>, >_Alloc = std::allocator<int>]' > >/s/unsup/include/g++-v3/ext/hash_map:173: instantiated from >`_Tp& std::hash_map<_Key, _Tp, _HashFcn, _EqualKey, >_Alloc>::operator[](typename std::hashtable<std::pair<const _Key, >_Tp>, _Key, _HashFcn, std::_Select1st<std::pair<const _Key, _Tp> > >>, _EqualKey, _Alloc>::key_type&) >> >[with _Key = std::string, >_Tp = int, >_HashFcn = std::hash<std::string>, >_EqualKey = std::equal_to<std::string>, >_Alloc = std::allocator<int>]' > >src/junk.cpp:7: instantiated from here >/s/unsup/include/g++-v3/ext/stl_hashtable.h:507: no match for >call to `(const std::hash<std::string>) (const std::basic_string<char, > std::char_traits<char>, std::allocator<char> >&)' > > >Thanks! >Matt > >------------------ >Matthew Sundling >sundlm@cs.wisc.edu > > > 看了上面三个资料后,我想你可以像使用一个map一样使用hash_map了。 转自 http://hi.baidu.com/lr02/blog/item/7aca821c2294f78787d6b6a5.html
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