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Generally, is there somewhere a good tutorial and examplefor the use of
SGI STL hash_set?
I am lost in SGI documentation.

More specifically, i am trying to use hat I need that a hash_set :

hash_set<c> h;

and logically the h function for my c class is missing and I get a
compile error.

How do I declare this hash function?

Pierre Couderc wrote:
> Generally, is there somewhere a good tutorial and examplefor the use of
> SGI STL hash_set?

I don't know, but you can get a tutorial for the very similar and
nearly standardized std::tr1::unordered_set in Pete Becker's book on
TR1.

> I am lost in SGI documentation.
>
> More specifically, i am trying to use hat I need that a hash_set :
>
> hash_set<c> h;
>
> and logically the h function for my c class is missing and I get a
> compile error.
>
> How do I declare this hash function?

You need to specialize the hash functor for your class:

#include <hash_set>

class C { /*...*/ };

// Hashable classes must have an == operator
// We'll just stub it out here, pending definition of C
bool operator==( const C&, const C& ) { return true; }

namespace std
{
template<> struct hash<C>
{
// Define the hash function. We'll just stub it out here.
size_t operator()( const C& ) const { return 0; }
};
}

void hash_set_test()
{
C c;
std::hash_set<C> hsc;
hsc.insert( c );
}

Cheers! --M

Thank you,
It is exactly the example that was missing me. I am sure that it will
be useful tou those who will be looking for "hash-set tutorial"...
The exact syntax of the hash function in not evident for me, even it it
should...
Thank you again,
Pierre



On Dec 28, 4:26 pm, "mlimber" <mlim...@gmail.com> wrote:
> Pierre Couderc wrote:
> > Generally, is there somewhere a good tutorial and examplefor the use of
> > SGI STL hash_set?I don't know, but you can get a tutorial for the very similar and
> nearly standardized std::tr1::unordered_set in Pete Becker's book on
> TR1.
>
> > I am lost in SGI documentation.
>
> > More specifically, i am trying to use hat I need that a hash_set :
>
> > hash_set<c> h;
>
> > and logically the h function for my c class is missing and I get a
> > compile error.
>
> > How do I declare this hash function?You need to specialize the hash functor for your class:
>
> #include <hash_set>
>
> class C { /*...*/ };
>
> // Hashable classes must have an == operator
> // We'll just stub it out here, pending definition of C
> bool operator==( const C&, const C& ) { return true; }
>
> namespace std
> {
> template<> struct hash<C>
> {
> // Define the hash function. We'll just stub it out here.
> size_t operator()( const C& ) const { return 0; }
> };
> }
>
> void hash_set_test()
> {
> C c;
> std::hash_set<C> hsc;
> hsc.insert( c );
> }
>
> Cheers! --M