Re: [SOLVED] Help migrating hash_set to c++0x

Paulo da Silva <>
Tue, 21 Dec 2010 04:25:06 +0000
Em 21-12-2010 03:37, Paulo da Silva escreveu:

Em 20-12-2010 22:59, Paulo da Silva escreveu:

I just saw (wikipedia for example) that unordered_set should implement
the same behaviour as that of hash_set. Neverthless it is not working in
this code!

#include <memory>
#include <unordered_set>
#include <iostream>

using namespace std;

class Foo
    string s;
    Foo(char const * const sc): s(sc) {}

class eqf
    inline bool operator()(Foo const &s1,Foo const &s2) const
    { return (s1.s==s2.s);

class hf
    inline size_t operator()(Foo const &x) const
    { return hash<char const *>()(x.s.c_str());

// typedef __gnu_cxx::hash_set<Foo,hf,eqf> MSet;
typedef unordered_set<Foo,hf,eqf> MSet;

int main()
{ MSet mc;
    pair<MSet::iterator,bool> r;
    // OK expected and obtained
    cout << "xxxx " << (r.second?"OK":"BAD") << endl;
    // Does not allow duplicates ...
    // BAD (duplicate) expected but OK obtained
    cout << "zzzz " << (r.second?"OK":"BAD") << endl;
    MSet::const_iterator it=mc.find(Foo("xxxx"));
    for (it=mc.begin();it!=mc.end();++it)
        cout << it->s << endl;
    return 0;

Anything wrong? Better way to implement?
Thanks for any comments.

Replacing class hf with this works.
class hf
    inline size_t operator()(Foo const &s) const
    { return hash<string const &>()(s.s);

I still don't understand why the previous example stopped to work!

Please correct me if I am wrong ...

I replaced hash_set by unordered_set. It seems that hash_set does not
exist using c++0x.

I am having the following problem:

pair<some_container::iterator,bool> r=ct_dir->insert(de);

When "de" already exists, with hash_table r.second contained false, but
using unordered_set r.second contains true, i.e. it accepts duplicates.

How do I fix this to avoid duplicates in the set and also be aware of that?


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