Tutorial and example to SGI STL hash_set

[Pierre Couderc]

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?

 

[mlimber]

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

 

[pierre]

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