实验6 模板类、文件I/O和异常处理

任务4

Vector.hpp

#pragma once

#include <iostream>
#include <stdexcept>

using namespace std;

template<typename T>
class Vector {
    public:
        Vector(int n,T value=0);
        ~Vector();
        Vector(const Vector<T> &v);
        int get_size() const;
        T& at(int i) ;
        T& operator[](int i);
        
        template<typename T1>
        friend void output(Vector<T1> &v);
        
        template<typename T2>
        friend void output(const Vector<T2> &v) ;
    private:
        T *arr;
        int length;
}; 

template<typename T>
Vector<T>::Vector(int n,T value): length{n} {
    if(n<0)
        throw length_error("长度不能为负！");
    arr = new T[n];
    for(int i=0;i<n;i++)
    {
        arr[i]=value;
    }
}

template<typename T>
Vector<T>::~Vector(){
    delete[] arr;
}

template<typename T>
Vector<T>::Vector(const Vector<T> &v){
    length=v.length;
    arr = new T[length];
    for(int i=0;i<length;i++)
    {
        arr[i]=v.arr[i];
    }
}

template<typename T>
int Vector<T>::get_size() const{
    return length;
}

template<typename T>
T& Vector<T>::at(int i) {
    if(i>=length)
        throw overflow_error("数组越界！");
    return arr[i];
}

template<typename T>
T& Vector<T>::operator[](int i){
    return arr[i];
}

template<typename T1>
void output( Vector<T1> &v){
    for(int i=0;i<v.length;i++)
    {
        cout<<v.arr[i]<<" ";
    }
    cout<<endl;
}

template<typename T2>
void output(const Vector<T2> &v) {
    for(int i=0;i<v.length;i++)
    {
        cout<<v.arr[i]<<" ";
    }
    cout<<endl;
}

task4.cpp

#include <iostream>
#include "Vector.hpp"

void test1() {
    using namespace std;

    int n;
    cout << "Enter n: ";
    cin >> n;
    
    Vector<double> x1(n);
    for(auto i = 0; i < n; ++i)
        x1.at(i) = i * 0.7;

    cout << "x1: "; output(x1);

    Vector<int> x2(n, 42);
    const Vector<int> x3(x2);

    cout << "x2: "; output(x2);
    cout << "x3: "; output(x3);

    x2.at(0) = 77;
    x2.at(1) = 777;
    cout << "x2: "; output(x2);
    cout << "x3: "; output(x3);
}

void test2() {
    using namespace std;

    int n, index;
    while(cout << "Enter n and index: ", cin >> n >> index) {
        try {
            Vector<int> v(n, n);
            v.at(index) = -999;
            cout << "v: "; output(v);
        }
        catch (const exception &e) {
            cout << e.what() << endl;
        }
    }
}

int main() {
    cout << "测试1: 模板类接口测试\n";
    test1();

    cout << "\n测试2: 模板类异常处理测试\n";
    test2();
}

运行结果

 

 

任务5

task5.cpp

#include <algorithm>
#include <iostream>
#include <iomanip>
#include <string>
#include <vector>
#include <fstream>

using std::string;
using std::vector;
using std::ostream;
using std::istream;
using std::setw;
using std::setprecision;
using std::setiosflags;
using std::ios_base;

class Score {
public:
    Score() = default;
    ~Score() = default;

    int get_score() const { return score; }
    string get_major() const { return major; }

    friend ostream& operator<<(ostream &out, const Score &c);
    friend istream& operator>>(istream &in, Score &c);

private:
    string no;          // 学号
    string name;        // 姓名
    string major;       // 专业
    int score;            // 分数 
};

ostream& operator<<(ostream &out, const Score &c) {
    out << setiosflags(ios_base::left);
    out << setw(15) << c.no
        << setw(15) << c.name
        << setw(15) << c.major
        << setw(5) << c.score;
    
    return out;
}

istream& operator>>(istream &in, Score &c) {
    in >> c.no >> c.name >> c.major >> c.score;

    return in;
}

bool compare_by_score(const Score &c1, const Score &c2) {
    if(c1.get_major()<c2.get_major())
        return true;
    
    if(c1.get_major()==c2.get_major())
        return c1.get_score() > c2.get_score();
    
    return false;
}

// 把对象中的元素插入到输出流out
void output(ostream &out, const vector<Score> &v) {
    for(auto &i: v)
        out << i << std::endl;
}


// 把对象中的元素写到filename文件中
void save(const string &filename, vector<Score> &v) {
    using std::ofstream;

    ofstream out(filename);
    if(!out.is_open()) {
        std::cout << "fail to open file to write\n";
        return;
    }

    output(out, v);
    out.close();
}

// 从文件filename读取对象
void load(const string &filename, vector<Score> &v) {
    using std::ifstream;

    ifstream in(filename);
    if(!in.is_open()) {
        std::cout << "fail to open file to read\n";
        return;
    }

    std::string title_line;
    getline(in, title_line);     // 跳过标题行

    Score t;
    while(in >> t) 
        v.push_back(t);

    in.close();
}

void test() {

    vector<Score> v;

    load("data5.txt", v);   
    sort(v.begin(), v.end(),compare_by_score); 
    output(std::cout, v);    // 输出对象v中信息到屏幕
    save("ans5.txt", v); 
}

int main() {
    test();
}

运行结果