Creating template class

[codefreaq]

I am new to c++. I have been trying to create a template class ADT but keep getting syntax error.I am stuck please look at my files and see whats wrong. thanks

header file:

#ifndef BOX
#define BOX

#include <list>
#include <string>

using namespace std;

//********************************************************************
//  
//          Class Declaration for box ADT
//
//********************************************************************

template<typename T>
class box{
      public :
             box();
             
             //constructs box object with user input size
             box(int userBoxSize);
             
             
             //accessors
             int getSize(); //returns the number of items in the box
             list<T> getItems();//returns a linked list of items in the box
             void printBox();
             //modifiers
             void emptyBox(); //empties the box
             T removeItem(T userItem);//parameters should say which items is to be removed
             void addItem(T userItem); // add an items to the box
             T checkReps(T userItem); //checks reps of item in box and returns the number
             void mergeBox(box userBox); //takes the box specified and merges it with box
             
             
             
      private :      
              int size,i,rep;
              list<T> boxList,tempList;
              list<T>:: iterator listIter,tempIter;
                     
      };



#endif

implementation:

#include<list>
#include<iostream>
#include"box.h"

//********************************************************
//
//  Implementation of box ADT
//
//********************************************************

//default constructor
template <typename T>
box<T>::box()
{}

//overloaded constructor
template <typename T>
box<T>::box(int userSize)
{
    list<T> boxList(userSize);
                                              
}

//accessor
template <typename T>
int box<T>::getSize()
{
    return boxList.size();        
}

list<T> box::getItems()
{
     return boxList<T>;
     
}

//modifiers

//empty box
template <typename T>
void box<T>::emptyBox()
{
     listIter<T> = boxList.begin();
     while(!boxList.empty())
     {
        boxList.erase(listIter); 
        listIter++;
     }     
}

//remove an item
template <typename T>
T box<T>::removeItem(int userItem)
{
    listIter = boxList.begin();
    while(*listIter != userItem)
    {
       listIter++;
    }
    boxList.erase(listIter);
}

//add an item
template <typename T>
void box<type>::addItem(T userItem)
{
   boxList.push_back(userItem);
}

//check reps

template <typename T>
type box<T>::checkReps(T userItem)
{
    rep=0;
    listIter = boxList.begin();
    while(listIter!= boxList.end())
    {
       if(*listIter == userItem)
       {
          rep++;
       }
       listIter++;
    }    
    return rep;
}

//merge box
template <typename T>
void box<T>::mergeBox(box userBox)
{
     tempList = userBox.getItems();
     tempIter = tempList.begin();
     while(!tempList.empty())
     {
        boxList.push_back(*tempIter);
        tempIter++;
        tempList.pop_front();
     }
}

//prtype box

template <typename T>
void box<T>::printBox()
{
     listIter = boxList.begin();
     cout<<"The number of items in the box is "<< boxList.size()<<"\n";
     
     i=0;
     while(i<boxList.size())
     {
        cout<<*listIter<<"  \n";
        listIter++;
        i++;
     } 
}

main file

#include <cstdlib>
#include <iostream>
#include"box.h"
using namespace std;

int main()
{
    box<int> mohs(10);
    mohs.addItem(2);
    mohs.addItem(4);
    mohs.addItem(6);
    mohs.addItem(8);
    mohs.addItem(12);
    mohs.addItem(12);
    mohs.printBox();
    
    cout<<endl;
    cout<<"number of repetitions of 12 : "<<mohs.checkReps(12)<<endl;
    
    box<int> hsn(5);
    hsn.addItem(3);
    hsn.addItem(5);
    hsn.addItem(7);
    hsn.addItem(9);
    hsn.printBox();
    
    
    mohs.mergeBox(hsn);
    mohs.printBox();
    mohs.removeItem(7);
    mohs.printBox();
    
    system("PAUSE");
    return EXIT_SUCCESS;
}

[Mybowlcut]

I am new to c++. I have been trying to create a template class ADT but keep getting syntax error.I am stuck please look at my files and see whats wrong. thanks

Err... if you already know what the error is, then tell us. Why should we try to find it when you know what it is?

[Peter_APIIT]

Post the error message here.

[codefreaq]

Err... if you already know what the error is, then tell us. Why should we try to find it when you know what it is?

sorry, I forgot

In file included from box.cpp:3:
box.h:40: error: expected `;' before "listIter"

box.cpp:31: error: `T' was not declared in this scope
box.cpp:31: error: template argument 1 is invalid
box.cpp:31: error: template argument 2 is invalid
box.cpp:31: error: `template<class T> class box' used without template parameters

box.cpp:32: error: ISO C++ forbids declaration of `getItems' with no type
box.cpp: In function `int getItems()':
box.cpp:33: error: `boxList' undeclared (first use this function)
box.cpp:33: error: (Each undeclared identifier is reported only once for each function it appears in.)
box.cpp:33: error: `T' undeclared (first use this function)
box.cpp:33: error: expected primary-expression before ';' token
box.cpp: In member function `void box<T>::emptyBox()':
box.cpp:43: error: `listIter' undeclared (first use this function)
box.cpp:43: error: expected primary-expression before '>' token
box.cpp:43: error: expected primary-expression before '=' token
box.cpp: At global scope:
box.cpp:54: error: prototype for `T box<T>::removeItem(int)' does not match any in class `box<T>'
box.h:30: error: candidate is: T box<T>::removeItem(T)

box.cpp:54: error: template definition of non-template `T box<T>::removeItem(int)'
box.cpp: In member function `T box<T>::removeItem(int)':
box.cpp:55: error: `listIter' undeclared (first use this function)
box.cpp: At global scope:
box.cpp:65: error: `type' was not declared in this scope
box.cpp:65: error: template argument 1 is invalid
box.cpp: In function `void addItem(T)':
box.cpp:67: error: `boxList' undeclared (first use this function)
box.cpp: At global scope:
box.cpp:73: error: expected constructor, destructor, or type conversion before "box"
box.cpp:73: error: expected `;' before "box"
box.cpp: In member function `void box<T>::mergeBox(box<T>)':
box.cpp:93: error: `tempIter' undeclared (first use this function)
box.cpp: In member function `void box<T>:rintBox()':
box.cpp:107: error: `listIter' undeclared (first use this function)

make.exe: *** [box.o] Error 1

Execution terminated

[Etherous]

Well, I'm not sure, but is it legal to have a space between 'list<T>::' and 'iterator' in box.h?

              list<T>:: iterator listIter,tempIter;

Edit:
Also, in box.cpp, you forgot the 'template<typename T>' for the method 'getItems', and the '<T>' after the 'box' in the definition of the same method, and when you return from the same method, you don't specify template type. That member's already been defined as having that template type.
The 'removeItem' method in the class definition takes type 'T' as a parameter, and the one in the implementation takes and 'int'
In implementation: 'void box<type>::addItem(T userItem)' should be changed to 'void box<T>::addItem(T userItem)'
In implementation: 'type box<T>::checkReps(T userItem)' should be changed to 'T box<T>::checkReps(T userItem)'

[codefreaq]

Thanks Etherous, I am still getting errors on instantiation of List iterators after removing the space between list<T>::iterator. This seems to be the only problem left.

In file included from box.cpp:3:
box.h:40: error: expected `;' before "listIter"
box.cpp:32: error: `template<class T> class box' used without template parameters
box.cpp: In function `std::list<T, std::allocator<_CharT> > getItems()':

box.cpp:34: error: `boxList' undeclared (first use this function)
box.cpp:34: error: (Each undeclared identifier is reported only once for each function it appears in.)
box.cpp: In member function `void box<T>::emptyBox()':
box.cpp:44: error: `listIter' undeclared (first use this function)
box.cpp:44: error: expected primary-expression before '>' token
box.cpp:44: error: expected primary-expression before '=' token
box.cpp: In member function `T box<T>::removeItem(T)':
box.cpp:56: error: `listIter' undeclared (first use this function)
box.cpp: In member function `T box<T>::checkReps(T)':
box.cpp:77: error: `listIter' undeclared (first use this function)

box.cpp: In member function `void box<T>::mergeBox(box<T>)':
box.cpp:94: error: `tempIter' undeclared (first use this function)
box.cpp: In member function `void box<T>:rintBox()':
box.cpp:108: error: `listIter' undeclared (first use this function)

make.exe: *** [box.o] Error 1

Execution terminated

[Etherous]

Oh the irony! Just maybe an hour ago I posted on this same forum with this same problem. On your line in box.h where you define your iterator members, change that line to this:

typename list<T>::iterator listIter,tempIter;

That should fix that problem.

Explanation: To avoid ambiguity in syntax for C++, any Qualified, dependent identifier is assumed to be a value, not a type. To explicitly tell C++ that 'list<T>::iterator' refers to a type, we must use the keyword 'typename'

[codefreaq]

great! that fixed it!

now I am getting linker errors. I think may not be calling box with the right syntax in my main

main.o(.text+0x187):main.cpp: undefined reference to `box<int>::box(int)'
main.o(.text+0x1a4):main.cpp: undefined reference to `box<int>::addItem(int)'
main.o(.text+0x1b7):main.cpp: undefined reference to `box<int>::addItem(int)'
main.o(.text+0x1ca):main.cpp: undefined reference to `box<int>::addItem(int)'
main.o(.text+0x1dd):main.cpp: undefined reference to `box<int>::addItem(int)'
main.o(.text+0x1f0):main.cpp: undefined reference to `box<int>::addItem(int)'

main.o(.text+0x203):main.cpp: more undefined references to `box<int>::addItem(int)' follow
main.o(.text+0x20e):main.cpp: undefined reference to `box<int>:rintBox()'
main.o(.text+0x235):main.cpp: undefined reference to `box<int>::checkReps(int)'
main.o(.text+0x284):main.cpp: undefined reference to `box<int>::box(int)'
main.o(.text+0x2a1):main.cpp: undefined reference to `box<int>::addItem(int)'
main.o(.text+0x2b4):main.cpp: undefined reference to `box<int>::addItem(int)'
main.o(.text+0x2c7):main.cpp: undefined reference to `box<int>::addItem(int)'
main.o(.text+0x2da):main.cpp: undefined reference to `box<int>::addItem(int)'
main.o(.text+0x2e5):main.cpp: undefined reference to `box<int>:rintBox()'
main.o(.text+0x319):main.cpp: undefined reference to `box<int>::mergeBox(box<int>)'
main.o(.text+0x3a8):main.cpp: undefined reference to `box<int>:rintBox()'

main.o(.text+0x3bb):main.cpp: undefined reference to `box<int>::removeItem(int)'
main.o(.text+0x3c6):main.cpp: undefined reference to `box<int>:rintBox()'
collect2: ld returned 1 exit status

make.exe: *** [box.exe] Error 1

Execution terminated

[ZuK]

Put your template implementations into the header or include them from the header.
Kurt

[Etherous]

Right. You have two options here:
1) (Easiest):
Include the box.cpp from either box.h or main.cpp, after the class itself is defined. I personally prefer the latter.

2) (More "Proper"):
Compile box.h and box.cpp as a library object (.o, .so, .a, .dll, .lib, etc.) and when you build the main.cpp, just include box.h. Then in the linking process, link main.o with box.o (or whatever extensions apply). This form is harder, but is considered more "proper" by "experts". Either way will work, though

Edit: Actually, Zuk has me here. Form two is out of the question here because, as he says, when it comes to templates, nothing is 'created' until it's used, so it's pointless to compile it separately.

[ZuK]

You cannot compile box.cpp. After all it is no actual code it's just a template and only becomes code when it is instantiated with some type.
Kurt