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Message: [QUOTE="Timo Qvist, post: 1520051"] Hi, I'm a bit new to STL and really new to SGI's hash_set implementation and I've having problem instantiating a hash_set with a custom hash function, I could really use some help sifting through g++ (v3.3.3) error message on this particular problem. I want a hash_set with class pointers as the hashed type, my class is simply called Transition, the following code doesn't work; using namespace __gnu_cxx; typedef struct _HashFunc : public unary_function<Transition *, size_t > { size_t operator()( const Transition *t ) const { return t->getID(); } } HashFunc; void foo( Transition *trans ) { hash_set< Transition *, hash<HashFunc> > my_hashset; // This far the compiler doesn't complain... myhashset.insert( trans ); // however, adding this instatiation causes the following error; } /usr/include/c++/3.3.3/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 = Transition*, _Key = Transition*, _HashFcn = __gnu_cxx::hash<HashFunc>, _ExtractKey = std::_Identity<Transition*>, _EqualKey = std::equal_to<Transition*>, _Alloc = std::allocator<Transition*>]': /usr/include/c++/3.3.3/ext/stl_hashtable.h:519: instantiated from `size_t __gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey, _Alloc>::_M_bkt_num(const _Val&, unsigned int) const [with _Val = Transition*, _Key = Transition*, _HashFcn = __gnu_cxx::hash<HashFunc>, _ExtractKey = std::_Identity<Transition*>, _EqualKey = std::equal_to<Transition*>, _Alloc = std::allocator<Transition*>]' /usr/include/c++/3.3.3/ext/stl_hashtable.h:884: instantiated from `void __gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey, _Alloc>::resize(unsigned int) [with _Val = Transition*, _Key = Transition*, _HashFcn = __gnu_cxx::hash<HashFunc>, _ExtractKey = std::_Identity<Transition*>, _EqualKey = std::equal_to<Transition*>, _Alloc = std::allocator<Transition*>]' /usr/include/c++/3.3.3/ext/stl_hashtable.h:378: instantiated from `std::pair<__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 = Transition*, _Key = Transition*, _HashFcn = __gnu_cxx::hash<HashFunc>, _ExtractKey = std::_Identity<Transition*>, _EqualKey = std::equal_to<Transition*>, _Alloc = std::allocator<Transition*>]' /usr/include/c++/3.3.3/ext/hash_set:175: instantiated from `std::pair<typename __gnu_cxx::hashtable<_Value, _Value, _HashFcn, std::_Identity<_Key>, _EqualKey, _Alloc>::const_iterator, bool> __gnu_cxx::hash_set<_Value, _HashFcn, _EqualKey, _Alloc>::insert(typename __gnu_cxx::hashtable<_Value, _Value, _HashFcn, std::_Identity<_Key>, _EqualKey, _Alloc>::value_type&) [with _Value = Transition*, _HashFcn = __gnu_cxx::hash<HashFunc>, _EqualKey = std::equal_to<Transition*>, _Alloc = std::allocator<Transition*>]' net.cpp:328: instantiated from here /usr/include/c++/3.3.3/ext/stl_hashtable.h:514: error: no match for call to `( const __gnu_cxx::hash<HashFunc>) (Transition* const&)' Ok, so I've figured out that somewhere deep down in the template we try and call the HashFunc operator() and we cant find a match, I just cant fix the HashFunc functor with the correct types for this to work? Or am I missing something? /tq [/QUOTE]

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