Copying templated vector
I currently have a vector using my template as its type:
vector<hashData> myTable;
hashData is a class:
class hashData{
public:
// constructor for hashData
hashData(hashType data){
this->data = data;
this->isActive = true;
this->deleted = false;
}
hashData(){
this->isActive = false;
this->deleted = false;
}
// internal data for hashTable
hashType data;
bool deleted;
bool isActive;
};
When I attempt to perform an operation such as the following:
vector<hashData> oldTable = myTable;
I receive this error message:
error C2440: 'initializing' : cannot convert from 'std::vector<_Ty>' to 'std::vector<_Ty>'
hashtable.h(211): error C2440: 'initializing' : cannot convert from 'std::vector<_Ty>' to> 'std::vector<_Ty>' with [_Ty=hashTable::hashData] and [_Ty=unsigned long]
No constructor could take the source type, or constructor overload resolution was ambiguous
Any ideas as to why this is occurring? My reference materials seem to think this is possible, so I'm not sure where my mistake is.
EDIT: Here is the complete header file of the hashTable implementation. I apologize for the length of the code, but I wanted to include everything since my initial "fragment" appears to be insufficient.
// Driver file #include "hashTable.h"
int main(void){
// hash table creation
hashTable<unsigned long> newTable(3);
// hash table insertion
newTable.addRecord(5);
newTable.addRecord(6);
newTable.addRecord(7);
newTable.addRecord(8);
}
// hashTable header file
// BEGIN HEADER FILE
#ifndef HASHTABLE_H
#define HASHTABLE_H
// Includes (system libraries)
#include <iostream>
#include <vector>
// Includes (custom libraries)
// Namespace
using namespace std;
// hashTable class
template <typename hashType>
class hashTable{
public:
// constructor
hashTable(int tableSize, string collisionMode = "Linear"){
this->myTable.resize(optimizeTableSize(tableSize));
this->collisionMode = collisionMode;
this->activeRecords = 0;
}
// hashTable operations
void addRecord(hashType);
void deleteRecord(hashType);
pair<bool,int> locateRecordPosition(hashType);
bool searchRecord(hashType);
hashType returnRecord(hashType);
// hashTable mainteance
void considerRehash();
void rehashTable();
int optimizeTableSize(int);
// hashTable math
bool isPrime(int);
int nextPrime(int);
// collision monitoring
void collisionLogUpdate(int, string);
int collisionLogAverage();
// hash table internal class
class hashData{
public:
// constructor for hashData
hashData(hashType data){
this->data = data;
this->isActive = true;
this->deleted = false;
}
hashData(){
this->isActive = false;
this->deleted = false;
}
// internal data for hashTable
hashType data;
bool deleted;
bool isActive;
};
private:
// hashing function
int calculateHash(hashType, int);
// hashTable data structure
vector<hashData> myTable;
int activeRecords;
// collision information
deque<pair<int, string> > collisionLog;
string collisionMode;
};
// hashTable implementation
// insert a record into the hash table
template <typename hashType>
void hashTable<hashType>::addRecord(hashType toAdd){
// search for the record
pair <bool, int> recordPos = locateRecordPosition(toAdd);
// analyze the results
if (recordPos.first == true) // the record already exists and is active
return;
// otherwise, go ahead and insert the record at this location
myTable[recordPos.second] = hashData(toAdd);
// update our count of active records
activeRecords++;
// consider a rehash of the hashTable
considerRehash();
}
// delete a record from the hash table
template <typename hashType>
void hashTable<hashType>::deleteRecord(hashType toDelete){
// search for the record
pair <bool, int> recordPos = locateRecordPosition(toDelete);
// analyze the results
if (recordPos.first == false) // the record does not exist -- there is nothing to delete here!
return;
// otherwise, go ahead and perform a shallow deletion at this area
myTable[recordPos.second].deleted = true;
// update our count of active records
activeRecords--;
// consider a rehash of the hashTable
considerRehash();
}
// find position of record within hash table (if such position exists)
template <typename hashType>
pair<bool,int> hashTable<hashType>::locateRecordPosition(hashType toFind){
// setup data structures
int collisionNum = 0;
unsigned int currentPos;
// search for the entry within the table
currentPos = calculateHash(toFind, myTable.size());
// enter a while loop for checking if we've found the item
while(myTable.at(currentPos).isActive && !myTable.at(currentPos).deleted){
// check to see if the entry found at the expected position matches
if(myTable.at(currentPos).data == toFind){
// update the collisionLog
collisionLogUpdate(collisionNum,"locateRecord");
// return the position of the item
return pair<bool, int>(true,currentPos); // we've successfully found the item
}
// otherwise, we need to look for the correct location
if (collisionMode == "Quadratic"){
currentPos += 2 * ++collisionNum - 1;
if(currentPos >= myTable.size())
currentPos -= myTable.size();
}
else if (collisionMode == "Linear"){
currentPos += 2 * ++collisionNum - 1;
if(currentPos >= myTable.size())
currentPos -= myTable.size();
}
// reloop and search again
}
// update the collisionLog
collisionLogUpdate(collisionNum,"locateRecord");
// if we escaped the loop, we were unable to find the item in the table -- return the first open location
return pair<bool, int>(false,currentPos); // we didn't find the item
}
// return whether a record exists within hash table
template <typename hashType>
bool hashTable<hashType>::searchRecord(hashType toFind){
return locateRecordPosition(toFind).first; // we didn't find the item
}
// return the contents of a record from the hash table
template <typename hashType>
hashType hashTable<hashType>::returnRecord(hashType toReturn){
if (locateRecordPosition(toReturn).first) // if the record actually exists
return myTable[locateRecordPosition(toReturn).second].data;
else
return hashType();
}
// calculate hash value
template <typename hashType>
int hashTable<hashType>::calculateHash(hashType toHash, int tableSize){
if (toHash < 0) // if we have a negative number, change it prior to hashing
toHash = (toHash*-1);
return ((toHash*37) % tableSize);
}
// review the collision log and consider rehashing
template <typename hashType>
void hashTable<hashType>::considerRehash(){
// check if we have used up more then half of the table, if we have, rehash
if((activeRecords + 1) > ((signed) myTable.size() / 2))
rehashTable();
// check the current average of collisions
// if the average number of collisions is greater then 20% of the table size (meaning it had to search through 20% of table), rehash
else if((collisionLogAverage() > (myTable.size() * .20)) && (myTable.size() >= 100))
rehashTable();
// check the last operations number of collisions
// if the number of collisions encounter is greater then 30% of the table size (meaning it had to search through 30% of table), rehash
else if((collisionLog.back().first > (myTable.size() * .30)) && (myTable.size() >= 100))
rehashTable();
}
// rehash the table
template <typename hashType>
void hashTable<hashType>::rehashTable(){
// make a copy of the existing vector
vector<hashType> oldTable = myTable;
// reallocate myTable
myTable.resize(optimizeTableSize(myTable.size() * 2)); // double the size of the current table
// clear myTable
myTable.clear();
// copy the existing table over
for (unsigned int i = 0; i < oldTable.size(); i++){
if(oldTable[i].isActive && !开发者_StackOverflow社区oldTable[i].deleted){
addRecord(oldTable[i].data);
}
}
}
// optimze table size
template <typename hashType>
int hashTable<hashType>::optimizeTableSize(int tableSize){
// if we are performing quadratic probing, we need to optimize the table size to be a prime number, to prevent loops
if (!isPrime(tableSize)){
return nextPrime(tableSize);
}
// we only need to bother with optimizing the table size IF we are performing quadratic probing
else
return tableSize;
}
// determine if prime number
template <typename hashType>
bool hashTable<hashType>::isPrime(int numberToEvaluate){
if(numberToEvaluate == 0)
return true;
numberToEvaluate = abs(numberToEvaluate);
if(numberToEvaluate % 2 == 0) return true;
for(int i = 3; i <= sqrt((float)numberToEvaluate); i+=2)
if(numberToEvaluate % i == 0)
return false;
return true;
}
// find the next prime number
template <typename hashType>
int hashTable<hashType>::nextPrime(int numberToEvaluate){
if (numberToEvaluate % 2 == 0)
numberToEvaluate++;
for (; !isPrime(numberToEvaluate); numberToEvaluate+=2)
;
return numberToEvaluate;
}
// update collision log with a new entry
template <typename hashType>
void hashTable<hashType>::collisionLogUpdate(int numberOfCollisions, string operationPerformed){
// add an entry to the log
collisionLog.push_back(pair<int,string>(numberOfCollisions, operationPerformed));
// verify we don't have more then 5 entires, if so, remove them
while(collisionLog.size() > 5)
collisionLog.pop_front();
}
template <typename hashType>
int hashTable<hashType>::collisionLogAverage(){
// add the last five entries, then take their average
// the log should be maxed at five entries.. so just add them all
// average holder
int average;
// loop through log
for (unsigned int i = 0; i < collisionLog.size(); i++){
average = collisionLog.at(i).first;
}
// average the sum
average = average/5;
// return the calculated average
return average;
}
// END HEADER FILE
#endif
myTable
is not a std::vector<hashData>
- Doublecheck it.
EDIT: After source posting.
vector<hashData> myTable;
vector<hashType> oldTable = myTable;
hashData != hashType
hashtable.h(211): error C2440: 'initializing' : cannot convert from 'std::vector<_Ty>' to> 'std::vector<_Ty>' with [_Ty=hashTable::hashData] and [_Ty=unsigned long]
See it looks like you do
std::vector<hashData> oldTable = myTable;
where myTable is std::vector<unsigned long>
, not std::vector<hashData>
.
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