C++ 模板类 My_vec

Posted 2023-02-21

【中文标题】C++ 模板类 My_vec

【英文标题】：C++ template class My_vec

【发布时间】：2014-09-12 21:24:01

【问题描述】：

我是一名学生，我正在为 C++ 中的数组做一个静态库，所以我不必每次上课都重写代码。

我在中学二年级，所以我不是专家。我希望我的代码与所有类型（int、float、ecc）兼容，但我遇到了一些麻烦。

你能看看我的代码吗？

我看过这个页面：Template (C++) - not sure if correct

My_vec.h

/*template My_vec.h
Ben Burk
Header file for a vector data structure.
*/

#include <ostream>

using namespace std;

template <typename T> class My_vec

    //member variables
    int size, capacity;
    T *ptr;

public:
    //member functions
    template <typename T> My_vec<T>::My_vec()
    
        size = 0; capacity = 10;
        ptr = new T[capacity];
    
    template <typename T> My_vec<T>::My_vec(const My_vec<T>& vec)
    
        if (!vec.is_empty())
        
            size = vec.size;
            capacity = vec.capacity;
            ptr = new T[capacity];

            for (int i = 0; i < capacity; i++)
                ptr[i] = vec.ptr[i];
        
    
    template <typename T> My_vec<T>::~My_vec()
    
        delete[] ptr;
    
    template <typename T> My_vec<T>& My_vec<T>::operator=(const My_vec<T>& vec)
    
        if (this == &vec)
            return *this;   

        this->size = vec.size; this->capacity = vec.capacity;
        this->ptr = new T[vec.capacity];

        for (int i = 0; i < this->capacity; i++)
            this->ptr[i] = vec.ptr[i];
    
    template <typename T> int My_vec<T>::get_size() const
    
        return size;
    
    template <typename T> int My_vec<T>::get_capacity() const
    
        return capacity;
    
    template <typename T> T& My_vec<T>::operator[](int i) const
    
        if (i < 0 || i > capacity)
        
            try  throw i; 
            catch (int e)
            
                cerr << "An exception occurred at index: " << e << '\n';
                cerr << "Index out of bounds\n";

              
        
        else
        
            return ptr[i];
        
    
    template <typename T> T& My_vec<T>::operator[](int i)
    
        if (i < 0 || i > capacity)
        
            try  throw i; 
            catch (int e)
            
                cerr << "An exception occurred at index: " << e << '\n';
                cerr << "Index out of bounds!\n";
            
        
        else
        
            return ptr[i];
        
    
    template <typename T> bool My_vec<T>::is_empty() const
    
        return (size == 0) ? 1 : 0;
    
    template <typename T> T& My_vec<T>::elem_at_rank(int r) const
    
        if (r <= 0 || r > capacity)
        
            try  throw r; 
            catch (int e)
            
                cerr << "An exception occurred at rank: " << e << '\n';
                cerr << "Element could not be found!\n";
            
        
        else
            return ptr[r-1];
    
    template <typename T> void My_vec<T>::insert_at_rank(int r, const T& elem)
    
        if (r <= 0 || r > capacity)
        
            try  throw r; 
            catch (int e)
            
                cerr << "An exception occurred at rank: " << e << '\n';
                cerr << "Element could not be inserted!\n";
            
        
        else
        
            if (size + 1 > capacity)
            
                capacity *= 2;
                ptr = new T[capacity];
            
            size++;

            for (int i = size - 1; i > r - 1; i--)
            
                ptr[i] = ptr[i-1];
            
            ptr[r-1] = elem;
        
    
    template <typename T> void My_vec<T>::replace_at_rank(int r, const T& elem)
    
        if (r <= 0 || r > capacity)
        
            try  throw r; 
            catch (int e)
            
                cerr << "An exception occurred at rank: " << e << '\n';
                cerr << "Element could not be replaced!\n";
            
        
        else
        
            if (ptr[r-1] == NULL)
                size++;

            ptr[r-1] = elem;
        
    
    template <typename T> void My_vec<T>::remove_at_rank(int r)
    
        if (r <= 0 || r > capacity)
        
            try  throw r; 
            catch (int e)
            
                cerr << "An exception occurred at rank: " << e << '\n';
                cerr << "Element could not be removed!\n";
            
        
        else
        
            for (int i = r-1; i < size; i++)
            
                ptr[i] = ptr[i+1];
            
            size--;
        
    
;

ostream& operator<<(ostream& out, const My_vec<T>& vec);
int find_max_index(const My_vec<T>& v, int size);
void sort_max(My_vec<T>& vec);

My_vec.cpp

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

using namespace std;

ostream& operator<<(ostream& out, const My_vec<T>& vec)
   
    out << "<";
    for (int x = 0; x < vec.get_capacity()-1; x++)
        out << vec[x] << ",";
    out << vec[vec.get_capacity()-1];
    out << ">\n";

int find_max_index(const My_vec<T>& v, int size)

    int i = -1;
    for (int x = 0; x < v.get_size(); x++)
    
        if (v[x+1] > v[x])
            i = x+1;
    
    return i;

void sort_max(My_vec<T>& vec)

    T c = NULL;
    for (int a = 0; a < vec.get_capacity(); a++)
    
        for (int x = 0; x < vec.get_capacity()-1; x++)
        
            if (vec[x+1] < vec[x])
            
                c = vec[x]; vec[x] = vec[x+1]; vec[x+1] = c;
               
        
    

编辑：我在编译以下文件时遇到问题。我的任务是创建一个可以采用多种变量类型 char、int、double 的类。我的问题是为什么我不能编译这个程序？

【问题讨论】：

SO 是一个问答网站，问题是什么？ P.S 如果这不是出于教育目的，C++ 已经有 std::vector。

My_vec<T> 定义中的所有template <typename T> My_vec<T>:: 都不是必需的；你应该删除它们。

This question 可能对您有用。

我否决了这个问题，因为您的代码充满了错误。这甚至不会编译。做好功课！

你能告诉我错误吗？

【参考方案1】：

从类中删除模板 My_vect::。 使全局函数模板函数，否则不能使用模板类作为参数。将它们的实现放入头文件中。 删除 My_vec.cpp，因为它不再包含任何代码。

你的头文件应该是这样的：

/*template My_vec.h
Ben Burk
Header file for a vector data structure.
*/

#include <iostream>

using namespace std;

template <typename T> class My_vec

    //member variables
    int size, capacity;
    T *ptr;

public:
    //member functions
    My_vec()
    
        size = 0; capacity = 10;
        ptr = new T[capacity];
    

    My_vec(const My_vec<T>& vec)
    
        if (!vec.is_empty())
        
            size = vec.size;
            capacity = vec.capacity;
            ptr = new T[capacity];

            for (int i = 0; i < capacity; i++)
                ptr[i] = vec.ptr[i];
        
    

    ~My_vec()
    
        delete[] ptr;
    

    My_vec& operator=(const My_vec<T>& vec)
    
        if (this == &vec)
            return *this;

        this->size = vec.size; this->capacity = vec.capacity;
        this->ptr = new T[vec.capacity];

        for (int i = 0; i < this->capacity; i++)
            this->ptr[i] = vec.ptr[i];
    

    int get_size() const
    
        return size;
    

    int get_capacity() const
    
        return capacity;
    

    T &operator[](int i) const
    
        if (i < 0 || i > capacity)
        
            try  throw i; 
            catch (int e)
            
                cerr << "An exception occurred at index: " << e << '\n';
                cerr << "Index out of bounds\n";

            
        
        else
        
            return ptr[i];
        
    

    T &operator[](int i)
    
        if (i < 0 || i > capacity)
        
            try  throw i; 
            catch (int e)
            
                cerr << "An exception occurred at index: " << e << '\n';
                cerr << "Index out of bounds!\n";
            
        
        else
        
            return ptr[i];
        
    

    bool is_empty() const
    
        return (size == 0) ? 1 : 0;
    

    T& elem_at_rank(int r) const
    
        if (r <= 0 || r > capacity)
        
            try  throw r; 
            catch (int e)
            
                cerr << "An exception occurred at rank: " << e << '\n';
                cerr << "Element could not be found!\n";
            
        
        else
            return ptr[r - 1];
    

    void insert_at_rank(int r, const T& elem)
    
        if (r <= 0 || r > capacity)
        
            try  throw r; 
            catch (int e)
            
                cerr << "An exception occurred at rank: " << e << '\n';
                cerr << "Element could not be inserted!\n";
            
        
        else
        
            if (size + 1 > capacity)
            
                capacity *= 2;
                ptr = new T[capacity];
            
            size++;

            for (int i = size - 1; i > r - 1; i--)
            
                ptr[i] = ptr[i - 1];
            
            ptr[r - 1] = elem;
        
    

    void replace_at_rank(int r, const T& elem)
    
        if (r <= 0 || r > capacity)
        
            try  throw r; 
            catch (int e)
            
                cerr << "An exception occurred at rank: " << e << '\n';
                cerr << "Element could not be replaced!\n";
            
        
        else
        
            if (ptr[r - 1] == NULL)
                size++;

            ptr[r - 1] = elem;
        
    

    void remove_at_rank(int r)
    
        if (r <= 0 || r > capacity)
        
            try  throw r; 
            catch (int e)
            
                cerr << "An exception occurred at rank: " << e << '\n';
                cerr << "Element could not be removed!\n";
            
        
        else
        
            for (int i = r - 1; i < size; i++)
            
                ptr[i] = ptr[i + 1];
            
            size--;
        
    
;

template <typename T>
ostream& operator<<(ostream& out, const My_vec<T>& vec)

    out << "<";
    for (int x = 0; x < vec.get_capacity() - 1; x++)
        out << vec[x] << ",";
    out << vec[vec.get_capacity() - 1];
    out << ">\n";


template <typename T>
int find_max_index(const My_vec<T>& v, int size)

    int i = -1;
    for (int x = 0; x < v.get_size(); x++)
    
        if (v[x + 1] > v[x])
            i = x + 1;
    
    return i;


template <typename T>
void sort_max(My_vec<T>& vec)

    T c = NULL;
    for (int a = 0; a < vec.get_capacity(); a++)
    
        for (int x = 0; x < vec.get_capacity() - 1; x++)
        
            if (vec[x + 1] < vec[x])
            
                c = vec[x]; vec[x] = vec[x + 1]; vec[x + 1] = c;
            
        
    

我想这是一个开始，但仍有很多清理工作要做，例如：

不应在头文件中使用 using namespace。

这是什么？

    try  throw r; 
    catch (int e)
    
        cerr << "An exception occurred at rank: " << e << '\n';
        cerr << "Element could not be found!\n";
    

使用这样的异常没有任何意义。

T& operator[](int i) const 函数。这应该返回 const T&，而不是 T&