How can I enable hash in C++ Standard Library?

Question

I have tried using #include<hash_map> and #include <hash_set> and I still get the same errors.

Here is my code:

void HashTable_chaining::remove( const string & x )
{
    int hash_index = hash( x, theLists.size( ) ) ;

    list<string>&  whichList = theLists[ hash_index ];

    // search to make sure element not present
    for(list<string>::iterator itr=whichList.begin();itr!=whichList.end();itr++) {
        if(*itr==x) {
            theLists[hash_index].erase(itr);
            return;
        }
    }
    // element not found - so nothing to remove
}

And my errors are:

Error   8   error C2872: 'hash' : ambiguous symbol  c:\users\aaron           johnson\desktop\program 5(johnson- noakes)\program 5(johnson- noakes)\chaining.cpp 32  1   Program 5(Johnson- Noakes)

And I have 8 of these errors. Any suggestions? How can I find out which headers have to be included to use hash?

Answer 1

Is hash a function of your own? If so, try putting it in a namespace of your own and then call the function like

int hash_index = yournamespace::hash( x, theLists.size() );

If you want to use the std::hash: It is defined in

#include <functional>

Answer 2

You can find the entire C++ spec here online, including our friend "std::hash":

http://en.cppreference.com/w/cpp/utility/hash

Answer 3

hash_set and hash_map is available in the SGI STL. Take a look at the following pages:

• http://www.sgi.com/tech/stl/hash_map.html
• http://www.sgi.com/tech/stl/hash_set.html

The documentation and source code is available at this link:

1. http://www.sgi.com/tech/stl/download.html