实验6 模板类、文件I/O和异常处理

4. 实验任务4

Vector.hpp

#pragma once 
#include<string>
#include<iostream>


using namespace std;

template<typename T>
class Vector {
public:
    Vector(int n);//构造函数
    Vector(int n, T vlaue);
    Vector(const Vector<T>& x);
    ~Vector();//析构函数

    T get_size()const;
    T& at(int index)const;
    T& at(int index);
    T& operator[](int index)const;
    T& operator[](int index);

    template<typename T1>
    friend void output(const Vector<T1>& x);

private:
    int size;
    T* ptr;
    int value;
};
template<typename T>
Vector<T>::Vector(int n) :size{ n } {
    if (n < 0)
        throw std::length_error("Vector constructor: negative size");
    ptr = new T[size];
}
template<typename T>
Vector<T>::Vector(int n, T vlaue) :size{n} {
    if (n < 0)
        throw std::length_error("Vector constructor: negative size");
    ptr = new T[size];
    for (int i = 0; i < size; ++i)
        ptr[i] = value;
}
template<typename T>
Vector<T>::Vector(const Vector<T>& x) :size{ x.size }, ptr{new int[size]} {
    for (int i = 0; i < size; ++i)
        ptr[i] = x.value;
}
template<typename T>
Vector<T>::~Vector() {
    delete[]ptr;
}
template<typename T>
T Vector<T>::get_size()const {
    return size;
}
template<typename T>
T& Vector<T>::at(int index)const {
    if (index < 0 || index >= size)
        throw std::out_of_range("Vector::at(): index out of this->size");
    return ptr[index];
}
template<typename T>
T& Vector<T>::at(int index) {
    return static_cast<const Vector*>(this)->at(index);
}
template<typename T>
T& Vector<T>::operator[](int index)const {
    if (index < 0 || index >= size)
        throw std::out_of_range("Vector::operator[]():index out of this->size");
    return ptr[index];
}
template<typename T>
T& Vector<T>::operator[](int index) {
    return static_cast<const Vector*>(this)->operator[](index);
}

template<typename T1>
void output(const Vector<T1>& x) {
    for (int i=0;i<x.size;++i)
        cout << x.ptr[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) { // 多组输入，按下Ctrl + Z终止
            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();
}

 

5. 实验任务5

task5.cpp

#include"students.hpp"
#include"utils.hpp"
#include<iostream>
#include<vector>
#include<algorithm>

void test() {
    using namespace std;

    vector<students>v;

    load("data5.txt", v);
    sort(v.begin(), v.end(), compare);
    output(cout, v);
    save("ans.txt", v);

}

int main() {
    test();
}

students.hpp

#pragma once 

#include<iostream>
#include<string>
#include<iomanip>

using namespace std;
using std::ostream;
using std::istream;
using std::setw;
using std::setprecision;
using std::setiosflags;
using std::ios_base;

//students
class students {
public:
    students() = default;
    ~students() = default;

    string get_major()const { return major; }
    float get_score()const { return score; }
    
    friend ostream& operator<<(ostream & out, const students &c);
    friend istream& operator>>(istream& in, students& c);

private:
    int no;//学号
    string name;
    string major;
    float score;
};

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

}

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

utils.hpp

#include"students.hpp"
#include<fstream>
#include<iostream>
#include<string>
#include<vector>

//排序函数
bool compare(const students& c1, const students& c2) {
    if (c1.get_major() != c2.get_major())
        return c1.get_major() < c2.get_major();
    return c1.get_score() > c2.get_score();
}

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

//把vector<students>对象中元素写入filename文件
void save(const std::string& filename, std::vector<students>& 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读取信息到vector<students>对象
void load(const std::string& filename, std::vector<students>& 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);

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

    in.close();
}