实验六 模板类，文件I/O和异常处理

任务4

代码：

Vector.hpp:

#pragma once
#include<iostream>
#include<stdexcept>
#include<cmath>

using namespace std;

template<typename T>
class Vector {
public:
    Vector(int s ) :size{ s } {
        if (s < 0)
            throw std::length_error("vector constructor:negative size");

        ptr = new T[size];
    }

    Vector(int s , T value ) :size{ s } {
        if (s < 0)
            throw std::length_error("vector constructor:negative size");

        ptr = new T[size];
        for (int i = 0; i < size; ++i)
            ptr[i] = value;
    }

    Vector(const Vector<T>& v) :size{ v.size }, ptr{ new T[size] } {
        for (int i = 0; i < size; ++i)
            ptr[i] = v.ptr[i];
    }

    ~Vector() { delete[]ptr; }

    int get_size() { return size; }
     
    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];
    }

    T& operator[](int index) {
        if (index < 0 || index >= size)
            throw std::out_of_range("vector::operator[]():index out of this->size");

        return ptr[index];
    }

    friend void output(const Vector<T>v) {
        for (int i = 0; i < v.size; i++)
            cout << v.at(i) << ",";
        cout << "\b\b\n";
    }

private:
    int size;
    T* ptr;
};

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);

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

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

运行结果：

任务5

代码：

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

using namespace std;

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

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

    friend ostream& operator<<(ostream& out, const student& s) {
        out << setiosflags(ios_base::left);
        out << setw(10) << s.number
            << setw(10) << s.name
            << setw(10) << s.major
            << setw(10) << s.score;

        return out;
    }

    friend istream& operator>>(istream& in,  student& s) {
        in >>s.number >> s.name >> s.major >> s.score;

        return in;
    }

private:
    string number;
    string name;
    string major;
    int score;

};

bool compare(const student& s1, const student& s2) {
    if (s1.get_major() < s2.get_major())
        return true;

    if (s1.get_major() == s2.get_major())
        return s1.get_score() > s2.get_score();

    return false;
}

void output(ostream& out, const vector<student>& v) {
    for (auto& i : v)
        out << i << endl;
}

void save(const string& filename, vector<student>& v) {
    ofstream out(filename);
    if (!out.is_open()) {
        cout << "fail to open file to write\n";
        return;
    }

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

void load(const string& filename, vector<student>& v) {
    ifstream in(filename);
    if (!in.is_open()) {
        cout << "fail to open to read\n";
        return;
    }

    string title_line;
    getline(in, title_line);

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

    in.close();
}

int main() {
    vector<student>v;

    load("data5.txt", v);
    sort(v.begin(), v.end(), compare);
    output(cout, v);
    save("ans5.txt", v);
}

运行结果：