Types and Templates

[Bomer911]

Help I dont know what Im doing wrong, so please tell me because I have this.

ArraList.h

#ifndef ARRAYLIST_H
#define ARRAYLIST_H
#define DEFAULT_MAX_SIZE 1024
#include <stdexcept>
using namespace std;

template <typename E>
class ArrayList
{
    private:
        E *elements;
        int max = DEFAULT_MAX_SIZE;
        int size;
        int pos;

    public:
        ArrayList(int pMax = DEFAULT_MAX_SIZE);
        virtual ~ArrayList();
        void insert(E pElement)throw(runtime_error);
        void append(E pElement)throw(runtime_error);
        E remove()throw(runtime_error);
        void clear();
        E getElement() throw(runtime_error);
        void goToStart();
        void goToEnd();
        void goToPos(int pPos)throw(runtime_error);
        void previous();
        void next();
        int getPos(){return pos;};
        int getSize(){return size;}
        void printList();

};

class template ArrayList<int>;
class template ArrayList<float>;
class template ArrayList<double>;

#endif // ARRAYLIST_H 

ArrayList.cpp

#include "ArrayList.h"
#include <iostream>

using namespace std;

template <typename E>
ArrayList<E>::ArrayList(int pMax){
    elements = new E[pMax];
    max = pMax;
    size = 0;
    pos = 0;
}

template <typename E>
ArrayList<E>::~ArrayList()
{
    delete [] elements;
}

template <typename E>
void ArrayList<E>::insert(E pElement) throw(runtime_error){
    if(size == max){
        throw runtime_error("List is full");
    }
    for (int i = size; i > pos; i--){
        elements[i] = elements[i-1];
    }
    elements[pos] = pElement;
    size++;
}

template <typename E>
void ArrayList<E>::append(E pElement) throw(runtime_error){
    if(size == max){
        throw runtime_error("List is full");
    }
    elements[size] = pElement;
    size++;
}

template <typename E>
E ArrayList<E>::remove() throw(runtime_error){
    if(size == 0){
        throw runtime_error("List is empty");
    }
    if((pos < 0) || (pos >= size)){
        throw runtime_error("Index out of bounds");
    }

    E temp = elements[pos];

    for (int i = pos; i < size-1; i++){
        elements[i] = elements[i+1];
    }
    size--;
    return temp;
}

template <typename E>
void ArrayList<E>::clear(){
    size = 0;
    pos = 0;
    delete [] elements;
    elements = new E[max];
}

template <typename E>
E ArrayList<E>::getElement() throw(runtime_error){
    if(size == 0){
        throw runtime_error("List is empty");
    }
    if(pos > size){
        throw runtime_error("No element");
    }
    return elements[pos];
}

template <typename E>
void ArrayList<E>::goToStart(){
    pos = 0;
}

template <typename E>
void ArrayList<E>::goToEnd(){
    pos = size;
}

template <typename E>
void ArrayList<E>::goToPos(int pPos) throw(runtime_error){
    if((pPos < 0) || (pPos > size)){
        throw runtime_error("Index out of bounds");
    }
    pos = pPos;
}

template <typename E>
void ArrayList<E>::previous(){
    if(pos > 0){
        pos--;
    }
}

template <typename E>
void ArrayList<E>::next(){
    if(pos < size){
        pos++;
    }
}

template <typename E>
void ArrayList<E>::printList(){

    goToStart();
    for(int j = 0; j < getSize(); j++){
        cout<<getElement()<<" "<<endl;
        next();
    }


}

main.cpp

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

int main()
{
    ArrayList<int> AL(10);//Error Here: error: variable 'ArrayList<int> AL' has initializer but incomplete type|
    for (int i=0;i<22;i++){
        AL.insert(i);
    }
    AL.printList();

    return 0;
}

I have been fighting so hard with those typenames because I dont usually use them. And now I dont know whats happening but I kinda guess that fixing must be so idiotic and I hate for not knowing the answer to it.

[TheIdeasMan]

Hi,

All of the templates must be in a header file.

Why do you have this ?

class template ArrayList<int>;
class template ArrayList<float>;
class template ArrayList<double>;

I was able to get it to compile without that.

A couple of other things:

I haven't seen throw used like this before:

template <typename E>
E ArrayList<E>::remove() throw(runtime_error){

[JLBorges]

> Why do you have this ?

An explicit instantiation definition (while template code is under development) helps catch errors early.

Syntax for explicit instantiation definition of the class template : template class ArrayList<int> ;

Ideally, place this outside the header, and also have an explicit instantiation definition for a non-trivial type.
For instance template class ArrayList<std::string> ;


> I haven't seen throw used like this before:

Dynamic exception specification. Deprecated in C++11 and may be removed in C++17.
http://en.cppreference.com/w/cpp/language/except_spec

[TheIdeasMan]

@JLBorges

Thanks, awesome as per usual :+)