hash function insert problems

I am trying to implement the insert function, which inserts a new value into a hash table.
I am getting a compile error though which doesn't make sense to me.

To outline my data structure, I have a hash_set which includes a vector<HashNode*> m_table. Each HashNode is constructed like a node in a doubly linked list, so each HashNode has a 'next' and 'prev' where the end node points to 0.

My compilation error is this.

Code:

hash_set.h: In member function ‘std::pair<hash_set<KeyType, HashFunc>::iterator, bool> hash_set<KeyType, HashFunc>::insert(const KeyType&)’:
hash_set.h:185: error: name lookup of ‘pt’ changed for new ISO ‘for’ scoping
hash_set.h:181: error:   using obsolete binding at ‘pt’

And here is my code.

Code:

//  Insert the key if it is not already there.
  std::pair< iterator, bool > insert( KeyType const& key )
  {
    const float LOAD_FRACTION_FOR_RESIZE = 1.25;

    //  Resize if necessary.
    if ( m_size >= LOAD_FRACTION_FOR_RESIZE * m_table.size() )
      this->resize_table( 2*m_table.size()+1 );  // making the new and old sizes relatively prime breaks up clusters


    if (find(key)==end()) 
      return std::make_pair(end(),false);
    else {

      unsigned int hash_value = m_hash(key);
      unsigned int index = hash_value%m_table.size();
      
      for (HashNode* pt = m_table[index];pt->next;pt=pt->next) {
	if (pt->key == key)
	  return std::make_pair(iterator(this,index,pt),false);
      }
      pt->key=key;
      return std::make_pair(iterator(this,index,pt),true);
    }
  }

> pt->key=key;
> return std::make_pair(iterator(this,index,pt),true);
pt is no longer in scope at this point, as it was declared within the above for-loop.

If you declare a variable in the for-loop intializer like the red bit, then you should not be using it after the end of the for-loop like the green bits:

Code:

      for (HashNode* pt = m_table[index];pt->next;pt=pt->next) {
	if (pt->key == key)
	  return std::make_pair(iterator(this,index,pt),false);
      }
      pt->key=key;
      return std::make_pair(iterator(this,index,pt),true);

--
Mats

how should I move to the end of the list to add a value then? I need to add the value at the end of the list if it doesn't find it. So basically it needs to add a value to pt after the for loop because pt moves to the end of the list.

I changed my code to this below which compiles and I believe it should work. When I ran some test code, I could not access .second for the pair returned. Do my return statements look correct? For some reason the bool at the end is not accessible.

The function returns a pair<iterator,bool>

Code:

for (HashNode* pt = m_table[index];pt->next;pt=pt->next) {
	if (pt->key == key)
	  return std::make_pair(iterator(this,index,pt),false);
        else if (!pt->next) {
          pt->next->key=key;
          return std::make_pair(iterator(this,index,pt),true);
         }
      }
      pt->key=key;
      return std::make_pair(iterator(this,index,pt),true);

No, move the HashNode *pt out of the for() statement - just before it is fine.

--
Mats

Thanks! I got it!
All good now with slight modifications.

Thanks again