数组类模板（中）

#ifndef _ARRAY_H_
#define _ARRAY_H_

template
< typename T, int N >
class Array
{
    T m_array[N];
public:
    int length();
    bool set(int index, T value);
    bool get(int index, T& value);
    T& operator[] (int index);
    T operator[] (int index) const;   //数组类对象有可能是const的，此时只能调用const成员函数。
    virtual ~Array();
};

template
< typename T, int N >
int Array<T, N>::length()
{
    return N;
}

template
< typename T, int N >
bool Array<T, N>::set(int index, T value)
{
    bool ret = (0 <= index) && (index < N);
    
    if( ret )
    {
        m_array[index] = value;
    }
    
    return ret;
}

template
< typename T, int N >
bool Array<T, N>::get(int index, T& value)
{
    bool ret = (0 <= index) && (index < N);
    
    if( ret )
    {
        value = m_array[index];
    }
    
    return ret;
}

template
< typename T, int N >
T& Array<T, N>::operator[] (int index)
{
    return m_array[index];
}

template
< typename T, int N >
T Array<T, N>::operator[] (int index) const   //既然是const的，这里只能返回值，不能返回引用。
{
    return m_array[index];
}

template
< typename T, int N >
Array<T, N>::~Array()
{

}

#endif

优化之前的IntArray类

#ifndef _HEAPARRAY_H_
#define _HEAPARRAY_H_

template
< typename T >
class HeapArray
{
private:
    int m_length;
    T* m_pointer;
    
    HeapArray(int len);
    HeapArray(const HeapArray<T>& obj);
    bool construct();
public:
    static HeapArray<T>* NewInstance(int length); 
    int length();
    bool get(int index, T& value);
    bool set(int index ,T value);
    T& operator [] (int index);
    T operator [] (int index) const;
    HeapArray<T>& self();
    ~HeapArray();   //因为上面的构造函数被定义成了private，说明我不希望被继承，因此就不需要写virtual了
};

template
< typename T >
HeapArray<T>::HeapArray(int len)
{
    m_length = len;
}

template
< typename T >
bool HeapArray<T>::construct()
{   
    m_pointer = new T[m_length];
    
    return m_pointer != NULL;
}

template
< typename T >
HeapArray<T>* HeapArray<T>::NewInstance(int length) 
{
    HeapArray<T>* ret = new HeapArray<T>(length);
    
    if( !(ret && ret->construct()) ) 
    {
        delete ret;
        ret = 0;
    }
        
    return ret;
}

template
< typename T >
int HeapArray<T>::length()
{
    return m_length;
}

template
< typename T >
bool HeapArray<T>::get(int index, T& value)
{
    bool ret = (0 <= index) && (index < length());
    
    if( ret )
    {
        value = m_pointer[index];
    }
    
    return ret;
}

template
< typename T >
bool HeapArray<T>::set(int index, T value)
{
    bool ret = (0 <= index) && (index < length());
    
    if( ret )
    {
        m_pointer[index] = value;
    }
    
    return ret;
}

template
< typename T >
T& HeapArray<T>::operator [] (int index)
{
    return m_pointer[index];
}

template
< typename T >
T HeapArray<T>::operator [] (int index) const
{
    return m_pointer[index];
}

template
< typename T >
HeapArray<T>& HeapArray<T>::self()
{
    return *this;
}

template
< typename T >
HeapArray<T>::~HeapArray()
{
    delete[]m_pointer;
}


#endif

#include <iostream>
#include <string>
#include "Array.h"
#include "HeapArray.h"

using namespace std;

int main()
{
    Array<double, 5> ad;
    
    for(int i=0; i<ad.length(); i++)
    {
        ad[i] = i * i;
    }
    
    for(int i=0; i<ad.length(); i++)
    {
        cout << ad[i] << endl;
    }
    
    cout << endl;
    
    HeapArray<char>* pai = HeapArray<char>::NewInstance(10);
    
    if( pai != NULL )
    {
        HeapArray<char>& ai = pai->self();
        
        for(int i=0; i<ai.length(); i++)
        {
            ai[i] = i + 'a';
        }
        
        for(int i=0; i<ai.length(); i++)
        {
            cout << ai[i] << endl;
        }
    }
    
    delete pai;
    
    return 0;
}

小结：
模板参数可以是数值型参数
数值型模板参数必须在编译期间唯一确定
数组类模板是基于数值型模板参数实现的
数组类模板是简易的线性表数据结构