C++Talk.NET

Luc Mazardo · Guest

The following code works with g++ 2.75 but
i've some troubles with compiling with g++ 3.0.

Thanks in advance if you have a solution.

Here is the error message.

main.hpp:28: specializing `struct std::hash<std::string>' in different
namespace
/usr/include/g++-v3/ext/stl_hash_fun.h:68: from definition of `template<class
_Key> struct std::hash'
make: *** [resource_identifier.lo] Error 1

#include <pair.h>
#include <string>
#include <map>
#include <vector>

#ifdef __GNUC__ /* grabbed in libstdc++ faq */
#if __GNUC__ < 3
#include namespace Sgi { using ::hash_map; }; // inherit globals
#else
#include <ext/hash_map>
#if __GNUC_MINOR__ == 0
namespace Sgi = std; // GCC 3.0
#else
namespace Sgi = ::__gnu_cxx; // GCC 3.1 and later
#endif
#endif
#else // ... there are other compilers, right?
namespace Sgi = std;
#endif

using namespace std;

//TODO: include this definition in the Hashtable class
template<> struct hash<string>
{
size_t operator()(const string& s) const
{
return hash<char const*>()(s.c_str());
}
};

#ifdef NAMESPACES
namespace foobar {
#endif

class NoSuchElementException
{
public:
NoSuchElementException(string w) {_what = w;}
virtual ~NoSuchElementException() {}
virtual string what() { return _what; }
private:
string _what;
};
template <class T> class Hashtable //: public ost::Conditional
{
public:
Hashtable() {} //: Conditional() {}

virtual ~Hashtable() {clear(); }
virtual T put(const string& key, T value)
{
assert(key.c_str() != NULL); //TODO: must throw ?

// enterMutex();
T returnValue = mHashtable[key];
mHashtable[key] = value;
// leaveMutex();

return returnValue;
}

virtual T get(const string& key) throw (NoSuchElementException)
{
assert(key.c_str() != NULL); //TODO: must throw ?
// enterMutex();

if (mHashtable.empty())
{
// leaveMutex ();
throw NoSuchElementException (key);
}

if (mHashtable.find(key) == mHashtable.end())
{
// leaveMutex();
throw NoSuchElementException(key);
}

T returnValue = mHashtable[key];
//leaveMutex();

return returnValue;
}
virtual void del(const string& key) throw (NoSuchElementException)
{
assert(key.c_str() != NULL); //TODO: must throw ?
// enterMutex();

if (mHashtable.find(key) == mHashtable.end()) {
// leaveMutex();
throw NoSuchElementException(key);
}
mHashtable.erase (key);
// leaveMutex();

return;
}
virtual void clear() {
// enterMutex();
mHashtable.erase(mHashtable.begin(), mHashtable.end());
// leaveMutex();
}

virtual bool isEmpty () {
bool ret;
// enterMutex();
ret = mHashtable.empty ();
// leaveMutex();
return ret;
}

virtual vector<pair toVector()
throw (NoSuchElementException)
{
vector <pair v;
// enterMutex();

if (mHashtable.empty()) {
// leaveMutex();
throw NoSuchElementException(string("hashtable is empty"));
}

for(hash_map<string, T , hash::iterator iter
= mHashtable.begin(); iter != mHashtable.end(); ++iter)
{
pair <string, T> p(*iter);// (iter->first, iter->second);
v.insert(v.begin(), p);
}

//leaveMutex();
return v;
}

protected:
hash_map<string, T, hash mHashtable;
};

int
main(void)
{
Hashtable<int> h;

return 0;
}
#ifdef NAMESPACES
}; // foobar
#endif

/** EMACS **
* Local variables:
* mode: c++
* c-basic-offset: 4
* End:
*/

Here is my release of g++ 3.0:
$ g++-3.0 -v
Reading specs from /usr/lib/gcc-lib/i386-linux/3.0.4/specs
Configured with: ../src/configure -v
--enable-languages=c,c++,java,f77,proto,objc
--prefix=/usr --infodir=/share/info --mandir=/share/mx
Thread model: posix
gcc version 3.0.4

Here is my release of g++ 2.95:
g++ -v
Reading specs from /usr/lib/gcc-lib/i386-linux/2.95.4/specs
gcc version 2.95.4 20011002 (Debian prerelease)

--
[email]Luc.Mazardo (AT) cvf (DOT) fr[/email]

Gianni Mariani · Guest

Luc Mazardo wrote:

Donovan Rebbechi · Guest

In article <bup1tt$d3 (AT) dispatch (DOT) concentric.net>, Gianni Mariani wrote:

Donovan Rebbechi · Guest

In article <m0oesw55nv.fsf (AT) beepbeep (DOT) dev33.cvf>, Luc Mazardo wrote:

Bret Pehrson · Guest

Gianni Mariani · Guest

Donovan Rebbechi wrote:

red floyd · Guest

Bret Pehrson wrote:

Donovan Rebbechi · Guest

In article <40101A38.4D3CC57E (AT) infowest (DOT) com>, Bret Pehrson wrote:

Rolf Magnus · Guest

Bret Pehrson wrote:

David Harmon · Guest

On Thu, 22 Jan 2004 19:44:41 GMT in comp.lang.c++, red floyd
<no.spam (AT) here (DOT) dude> was alleged to have written:

tom_usenet · Guest

On Thu, 22 Jan 2004 23:07:42 +0100, Rolf Magnus <ramagnus (AT) t-online (DOT) de>
wrote:

Bret Pehrson · Guest

Not a troll.

Let me maybe qualify my statement:

Resuable (non-template) classes should seriously consider all non-private
methods as virtual.

Reason for my statement: I'm tired of using class libraries that impose all
sorts of arbitrary restrictions because methods aren't virtual (but should be).

I'd rather that a class was needlessly loaded down w/ virtual methods than not.

tom_usenet wrote:

Bret Pehrson · Guest

Why is do_work protected?

The **ONLY** reason that something should be declared protected is to indicate
that the class is suitable for derivation, and that method has some potential
value to the derived class.

red floyd wrote:

Bret Pehrson · Guest

I'd be interested to hear why a virtual function should be private.

Let me expand a little: every (non-template) class that isn't expressly not
intended for derivation should by default have all non-private methods declared
virtual.

How many times have you used a class outside of your direct source manipulation
control (library or otherwise) that didn't have one or more virtual methods,
but that was suitable for derivation? Let's discuss the hacks that must be
used to attempt to overcome this in code...

Rolf Magnus wrote:

lilburne · Guest

Bret Pehrson wrote: