Template Errors

[stoneJax]

I have an assignment (below) where I need to modify a program so that it does not allow duplicate elements. I am given 4 files to work with and I can't even begin to modify them because I am getting some kind of template errors after trying to set up the files.

Error:
Severity Code Description Project File Line Suppression State
Error (active) E0864 vector is not a template Project28

Textbook If anyone wants to see it.
https://fall14cs.files.wordpress.com/2016/03/data-abstraction-and-problem-soving-with-c.pdf

Assignment:
The problem refers to Programming Problem 5 of Chapter 1, which you didn't do, but it was just writing out specifications for a "Set" ADT, which is just a slight variation on the "Bag" ADT. Your task this week is to write an "ArraySet" class to implement the "Set" ADT. You don't need to write out the specifications.

The vast majority of your code will be copied directly from the ArrayBag class of chapter 3. You just need to make minor adjustments to reflect the fact that duplicate elements are not allowed. (Note that you will receive 0 if your submitted code allows duplicate elements, since this is pretty much the only thing we are changing.) Also, we won't have a frequencyOf() member function.

Your ArraySet class must be derived from a "SetInterface" abstract class. There's almost no work for you to do here. Just copy the "BagInterface" class from chapter 1. None of the code in that abstract class will need to be modified, except that the frequencyOf() member function will be removed. If you find the part about deriving the class from "SetInterface" confusing, be sure to ask about it in the discussion!

Here is the source code from the text that you are to use as a starting point:

ArrayBag.cpp
ArrayBag.h
BagInterface.h
bagtester.cpp


4 given files:

 
#ifndef ARRAY_BAG_
#define ARRAY_BAG_


template<class ItemType>
class ArrayBag : public BagInterface<ItemType>
{
private:
	static const int DEFAULT_CAPACITY = 6; // Small size to test for a full bag
	ItemType items[DEFAULT_CAPACITY];      // Array of bag items
	int itemCount;                         // Current count of bag items 
	int maxItems;                          // Max capacity of the bag

	// Returns either the index of the element in the array items that
	// contains the given target or -1, if the array does not contain 
	// the target.
	int getIndexOf(const ItemType& target) const;

public:
	ArrayBag();
	int getCurrentSize() const;
	bool isEmpty() const;
	bool add(const ItemType& newEntry);
	bool remove(const ItemType& anEntry);
	void clear();
	bool contains(const ItemType& anEntry) const;
	int getFrequencyOf(const ItemType& anEntry) const;
	vector<ItemType> toVector() const;
}; 

#endif




#ifndef BAG_INTERFACE_
#define BAG_INTERFACE_

#include <vector>

template<class ItemType>
class BagInterface
{
public:

	virtual int getCurrentSize() const = 0;

        virtual bool isEmpty() const = 0;

	virtual bool add(const ItemType& newEntry) = 0;

	virtual bool remove(const ItemType& anEntry) = 0;

	virtual void clear() = 0;

	virtual int getFrequencyOf(const ItemType& anEntry) const = 0;

	virtual bool contains(const ItemType& anEntry) const = 0;

	virtual std::vector<ItemType> toVector() const = 0;

	virtual ~BagInterface() { }
}; 





#include <iostream>
#include "ArrayBag.h"
#include "BagInterface.h"
#include <vector>

template<class ItemType>
bool ArrayBag<ItemType>::add(const ItemType& newEntry)
{
	bool hasRoomToAdd = (itemCount < maxItems);
	if (hasRoomToAdd)
	{
		items[itemCount] = newEntry;
		itemCount++;
	}  // end if

	return hasRoomToAdd;
} 



template<class ItemType>
ArrayBag<ItemType>::ArrayBag() : itemCount(0), maxItems(DEFAULT_CAPACITY)
{
}  



template<class ItemType>
int ArrayBag<ItemType>::getCurrentSize() const
{
	return itemCount;
}  


template<class ItemType>
bool ArrayBag<ItemType>::isEmpty() const
{
	return itemCount == 0;
} 




template<class ItemType>
vector<ItemType> ArrayBag<ItemType>::toVector() const
{
	std::vector<ItemType> bagContents;
	for (int i = 0; i < itemCount; i++)
		bagContents.push_back(items[i]);

	return bagContents;
} 




template <class ItemType>
bool ArrayBag<ItemType>::contains(const ItemType & anEntry) const
{
	bool isFound = false;
	int curIndex = 0; // Current array index
	while (!isFound && (curIndex < itemCount))
	{
		isFound = (anEntry == items[curIndex]);
		if (!isFound)
			curIndex++; // Increment to next entry
	} 

	return isFound;
}




template<class ItemType>
void ArrayBag<ItemType>::clear()
{
	itemCount = 0;
}  // end clear





template<class ItemType>
int ArrayBag<ItemType>::getIndexOf(const ItemType & target) const
{
	bool isFound = false;
	int result = -1;
	int searchIndex = 0;

	
	while (!isFound && (searchIndex < itemCount))
	{
		isFound = (items[searchIndex] == target);
		if (isFound)
		{
			result = searchIndex;
		}
		else
		{
			searchIndex++;
		}  
	}  

	return result;
}  






template<class ItemType>
bool ArrayBag<ItemType>::remove(const ItemType & anEntry)
{
	int locatedIndex = getIndexOf(anEntry);
	bool canRemoveItem = !isEmpty() && (locatedIndex > -1);
	if (canRemoveItem)
	{
		itemCount--;
		items[locatedIndex] = items[itemCount];
	}  

	return canRemoveItem;
} 








template<class ItemType>
int ArrayBag<ItemType>::getFrequencyOf(const ItemType & anEntry) const
{
	int frequency = 0;
	int curIndex = 0;       // Current array index
	while (curIndex < itemCount)
	{
		if (items[curIndex] == anEntry)
		{
			frequency++;
		}  

		curIndex++;          
	} 

	return frequency;
} 






#include <iostream>
#include <string>
#include "ArrayBag.h"
#include "BagInterface.h"
#include <vector>

using std::cout;
using std::endl;
using std::string;

void displayBag(ArrayBag<std::string>& bag)
{
	cout << "The bag contains " << bag.getCurrentSize()
		<< " items:" << endl;
	std::vector<string> bagItems = bag.toVector();

	int numberOfEntries = (int)bagItems.size();
	for (int i = 0; i < numberOfEntries; i++)
	{
		cout << bagItems[i] << " ";
	} 
	cout << endl << endl;
} 


void bagTester(ArrayBag<string>& bag)
{
	cout << "isEmpty: returns " << bag.isEmpty()
		<< "; should be 1 (true)" << endl;
	displayBag(bag);

	std::string items[] = { "one", "two", "three", "four", "five", "one" };
	cout << "Add 6 items to the bag: " << endl;
	for (int i = 0; i < 6; i++)
	{
		bag.add(items[i]);
	}  // end for

	displayBag(bag);

	cout << "isEmpty: returns " << bag.isEmpty()
		<< "; should be 0 (false)" << endl;

	cout << "getCurrentSize: returns " << bag.getCurrentSize()
		<< "; should be 6" << endl;

	cout << "Try to add another entry: add(\"extra\") returns "
		<< bag.add("extra") << endl;

	cout << "contains(\"three\"): returns " << bag.contains("three")
		<< "; should be 1 (true)" << endl;
	cout << "contains(\"ten\"): returns " << bag.contains("ten")
		<< "; should be 0 (false)" << endl;
	cout << "getFrequencyOf(\"one\"): returns "
		<< bag.getFrequencyOf("one") << " should be 2" << endl;
	cout << "remove(\"one\"): returns " << bag.remove("one")
		<< "; should be 1 (true)" << endl;
	cout << "getFrequencyOf(\"one\"): returns "
		<< bag.getFrequencyOf("one") << " should be 1" << endl;
	cout << "remove(\"one\"): returns " << bag.remove("one")
		<< "; should be 1 (true)" << endl;
	cout << "remove(\"one\"): returns " << bag.remove("one")
		<< "; should be 0 (false)" << endl;
	cout << endl;

	displayBag(bag);

	cout << "After clearing the bag, ";
	bag.clear();
	cout << "isEmpty: returns " << bag.isEmpty()
		<< "; should be 1 (true)" << endl;
} 
int main()
{
	ArrayBag<std::string> bag;
	cout << "Testing the Array-Based Bag:" << endl;
	cout << "The initial bag is empty." << endl;
	bagTester(bag);
	cout << "All done!" << endl;

	return 0;
} 

[stoneJax]

I played around with the code some. Now I am getting an error in the ArrayBag class on the line where the vector is. The error says I am missing a semi colon but it doesn't make sense to put one before the angle bracket in the prototype of a vector, nor does it work if I try it.

Error:
Severity Code Description Project File Line Suppression State
Error C2143 syntax error: missing ';' before '<' Project28

template<class ItemType>
class ArrayBag : public BagInterface<ItemType>
{
private:
	static const int DEFAULT_CAPACITY = 6; // Small size to test for a full bag
	ItemType items[DEFAULT_CAPACITY];      // Array of bag items
	int itemCount;                         // Current count of bag items 
	int maxItems;                          // Max capacity of the bag

	// Returns either the index of the element in the array items that
	// contains the given target or -1, if the array does not contain 
	// the target.
	int getIndexOf(const ItemType& target) const;

public:
	ArrayBag();
	int getCurrentSize() const;
	bool isEmpty() const;
	bool add(const ItemType& newEntry);
	bool remove(const ItemType& anEntry);
	void clear();
	bool contains(const ItemType& anEntry) const;
	int getFrequencyOf(const ItemType& anEntry) const;
	vector <ItemType> toVector() const;
}; 

[coder777]

Your problem with the vector has to do with the missing std:: in front of the vector.

That you do not include the definition of a type before you use it may cause several problems. E.g. you do not #inlcude BagInterface.h when use it in ArrayBag.

[stoneJax]

Okay thank you, I got that straightened out.

I am confused as to how we are supposed to organize the files when doing a template class. Are we supposed to put main, the implementation file, and the header file all in one? Or, are the implementation file and header file combined into one file and main in another? Also, the instructor has two implementation files and that confuses me because I have never seen more than one per program.

One may wonder why these questions aren't answered in class. This is an online class and the help I get is very minimal.

[coder777]

The rule of thumb: When you use something from another file #include that header file. This applies to templates as much as for other.

Are we supposed to put main, the implementation file, and the header file all in one?

That would certainly not a good strategy.

templates are header only hence you just include them where they are needed. In this regard the handling of templates is a bit simpler. You do not need an implementation file.

For non template files you have mostly one implementation file per header.

[stoneJax]

I think I got my files working. Thank you coder 777.