实验6 模板类、文件I/O和异常处理

1.实验任务4

Vector.hpp

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

using namespace std;

template<typename T>
class Vector {
public:
    Vector(int n); 
    Vector(int n, T value);
    Vector(const Vector<T>& vi);
    ~Vector();  

    int get_size() const; 
    T& at(int index) const; 
    T& at(int index); 

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

    template<typename U>
    friend void output(const Vector<U>& vi);

private:
    int size; 
    T* ptr;     
};

template<typename T>
void output(const Vector<T>& vi) {
    for(int i=0;i<vi.size;i++) { 
        cout<<vi.at(i)<<", "; 
    }
    cout<<endl;
}

template<typename T>
Vector<T>::Vector(int n):size(n) {
    if(n<0)
        throw length_error("Vector constructor: negative size");

    ptr=new T[size];
}

template<typename T>
Vector<T>::Vector(int n, T value) : size(n) {
    if(n<0)
        throw 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>& vi):size(vi.size),ptr(new T[size]) { 
    for(int i=0;i<size;i++) { 
        ptr[i]=vi.ptr[i];
    }
}

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

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

template<typename T>
T& Vector<T>::at(int index) const {
    if(index<0||index>=size) {
        throw out_of_range("Vector::at(): index out of range");
    }
    return ptr[index]; 
}

template<typename T>
T& Vector<T>::at(int index) {
    return const_cast<T&>(static_cast<const Vector<T>*>(this)->at(index)); 
}

template<typename T>
T& Vector<T>::operator[](int index) const {
    if (index < 0 || index >= size) {
        throw out_of_range("Vector::operator[](): index out of range");
    }
    return ptr[index]; 
}

template<typename T>
T& Vector<T>::operator[](int index) {
    return const_cast<T&>(static_cast<const Vector<T>*>(this)->operator[](index));
}

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();
}

结果截图：

 

2.实验任务5

task5.cpp

#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);
}

结果截图：