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ambigous symbol

genclik27 (24)
What does that mean?

error C2872: 'hash' : ambiguous symbol could be 'hash' or c:\program files (x86)\microsoft visual studio 10.0\vc\include\xfunctional(763) : std::hash'

Here is my code.

Hash_table.h
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template <typename HashedObj>
class HashTable
{
  public:
    explicit HashTable( int size = 101 ) : array( nextPrime( size ) )
      { makeEmpty( ); }

    bool contains( const HashedObj & x ) const
    {
        return isActive( findPos( x ) );
    }

    void makeEmpty( )
    {
        currentSize = 0;
        for( size_t i = 0; i < array.size( ); i++ )
            array[ i ].info = EMPTY;
    }

    bool insert( const HashedObj & x )
    {
            // Insert x as active
        unsigned currentPos = findPos( x );
        if( isActive( currentPos ) )
            return false;

        array[ currentPos ] = HashEntry( x, ACTIVE );

            // Rehash; see Section 5.5
        if( ++currentSize > array.size( ) / 2 )
            rehash( );

        return true;
    }

    bool remove( const HashedObj & x )
    {
        int currentPos = findPos( x );
        if( !isActive( currentPos ) )
            return false;

        array[ currentPos ].info = DELETED;
        return true;
    }

    enum EntryType { ACTIVE, EMPTY, DELETED };

  private:
    struct HashEntry
    {
        HashedObj element;
        EntryType info;

        HashEntry( const HashedObj & e = HashedObj( ), EntryType i = EMPTY )
          : element( e ), info( i ) { }
    };
    
    vector<HashEntry> array;
    unsigned currentSize;

    bool isActive( int currentPos ) const
      { return array[ currentPos ].info == ACTIVE; }

    int findPos( const HashedObj & x ) const
    {
        int offset = 1;
        unsigned currentPos = myhash( x );

        while( array[ currentPos ].info != EMPTY &&
                array[ currentPos ].element != x )
        {
            currentPos += offset;  // Compute ith probe
            offset += 2;
            if( currentPos >= array.size( ) )
                currentPos -= array.size( );
        }

        return currentPos;
    }

    void rehash( )
    {
        vector<HashEntry> oldArray = array;

            // Create new double-sized, empty table
        array.resize( nextPrime( 2 * oldArray.size( ) ) );
        for( unsigned j = 0; j < array.size( ); j++ )
            array[ j ].info = EMPTY;

            // Copy table over
        currentSize = 0;
        for( unsigned i = 0; i < oldArray.size( ); i++ )
            if( oldArray[ i ].info == ACTIVE )
                insert( oldArray[ i ].element );
    }
	int myhash( const HashedObj & x ) const
	{
		int hashVal = hash( x );

		hashVal %= array.size( );
		if( hashVal < 0 )
			hashVal += array.size( );

		return hashVal;
	}

};

int hash( int key )
{
	return key;
}

/**
* A hash routine for string objects.
*/

template <typename HashedObj>
int hash( const HashedObj & key )
{
	int hashVal = 0;

	for( unsigned i = 0; i < key.length( ); i++ )
		hashVal = 37 * hashVal + key[ i ];

	return hashVal;
}
#endif


SamuelAdams (1535)
you have int hash on line 109 and 119.
genclik27 (24)
It has to overload this functions. I do not think that error is about it. Anyway, I tried to delete one of them but nothing changes. Still get same error.
Peter87 (11178)
This can easily happen when you use using namespace std;. The compiler doesn't know if you mean std::hash or your hash function.
Last edited on
genclik27 (24)
I always use using namespace std;, if I change it I need to correct lots of thing by using std:: everywhere. Isn't there anyway to fix this without removing using namespace std;?
Peter87 (11178)
You could refer to your hash function as ::hash.
int hashVal = ::hash( x );

.. or use a different function name.
Last edited on
genclik27 (24)
Thank you very much, when I add it, it is solved.
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