实验6 模板类和文件I/O
1.
程序源码
task1
#include <iostream> #include <fstream> #include "Complex.hpp" void test1() { using namespace std; Complex<double> c1{1, 2}, c2; cout << "Enter c2: "; cin >> c2; cout << "c1 = " << c1 << endl; cout << "c2 = " << c2 << endl; cout << "c1 + c2 = " << c1 + c2 << endl; c1 += c2; cout << "c1.real = " << c1.get_real() << endl; cout << "c1.imag = " << c1.get_imag() << endl; cout << boolalpha << (c1 == c2) << endl; } void test2() { using namespace std; ofstream out; out.open("ans.txt"); if(!out.is_open()) { cout << "fail to open file ans.txt to write\n"; return; } Complex<int> c1{1, 9}, c2{8, 4}; out << "c1 = " << c1 << endl; out << "c2 = " << c2 << endl; out << "c1 + c2 = " << c1 + c2 << endl; out.close(); } int main() { using namespace std; cout << "test template Class Complex<T>....\n"; test1(); cout << "\ntest FILE I/O...\n"; test2(); }
Complex.hpp
#pragma once #include <iostream> using std::cout; using std::endl; using std::ostream; using std::istream; // declaration of template class template<typename T> class Complex { public: Complex(T r = 0, T i = 0): real{r}, imag{i} {} Complex(const Complex<T> &c): real{c.real}, imag {c.imag} {} T get_real() const { return real; } T get_imag() const { return imag; } Complex<T>& operator+=(const Complex<T> c1); template<typename T1> friend ostream &operator<<(ostream &out, const Complex<T1> &c1); template<typename T1> friend istream &operator>>(istream &in, Complex<T1> &c1); private: T real; T imag; }; // definition of template class // ----------------member function---------------- // overload operator+=, support operation such as c1 += c2 template<typename T> Complex<T>& Complex<T>::operator+=(const Complex<T> c1) { real += c1.real; imag += c1.imag; return *this; } // ---------------general function----------------- // overload operator+, support operation such as c1 + c2 template<typename T> Complex<T> operator+(const Complex<T> &c1, const Complex<T> &c2) { return Complex<T>(c1.get_real() + c2.get_real(), c1.get_imag() + c2.get_imag()); } // overload operator==, support operation such as c1 == c2 template<typename T> bool operator==(const Complex<T> &c1, const Complex<T> &c2) { return c1.get_real() == c2.get_real() && c1.get_imag() == c2.get_imag(); } //--------------------friend function--------------- // overload operator<<, support operation such as cout << c1 << endl; template<typename T1> ostream &operator<<(ostream &out, const Complex<T1> &c1) { if(c1.imag == 0) out << c1.real; else if(c1.imag > 0) out << c1.real << " + " << c1.imag << "i"; else out << c1.real << " - " << -c1.imag << "i"; return out; } // overload operator>>, support operation such as cin >> c1 >> c2 template<typename T1> istream &operator>>(istream &in, Complex<T1> &c1) { in >> c1.real >> c1.imag; return in; }
测试运行结果截图
2.实验任务2
task2.cpp
#include "stu.hpp" #include "utils.hpp" #include <vector> #include <fstream> #include <algorithm> int main() { using namespace std; vector<STU> stu; STU t; ifstream in; in.open("data.txt", ios::in); if(!in.is_open()) { cout << "fail to open file data.txt\n"; return 1; } while(in >> t) stu.push_back(t); in.close(); // ouput original stu info to screen cout << endl << "original info: " << endl; output(cout, stu); // sort by no // save to file data_by_no.txt sort(stu.begin(), stu.end(), compare_by_no); save("data_by_no.txt", stu); // sort by name // save to file data_by_name.txt sort(stu.begin(), stu.end(), compare_by_name); save("data_by_name.txt", stu); // sort by score, in decending order // output to file data_by score sort(stu.begin(), stu.end(), compare_by_score); save("data_by_score.txt", stu); }
stu.hpp
#pragma once #include <iostream> #include <iomanip> #include <string> using std::string; using std::ostream; using std::istream; using std::setw; using std::setiosflags; using std::ios_base; class STU{ public: STU() = default; ~STU() = default; string get_name() const { return name; } string get_no() const { return no; } int get_score() const { return score; } friend ostream& operator<<(ostream &out, const STU &s); friend istream& operator>>(istream &in, STU &s); private: string no; string name; int score; }; ostream& operator<<(ostream &out, const STU &s) { out << setiosflags(ios_base::left) << setw(15) << s.no << setw(15) << s.name << s.score; return out; } istream& operator>>(istream &in, STU &s) { in >> s.no >> s.name >> s.score; return in; }
utils.hpp
#include "stu.hpp" #include <vector> #include <fstream> #include <iostream> bool compare_by_name(const STU &s1, const STU &s2) { return s1.get_name() < s2.get_name(); } bool compare_by_no(const STU &s1, const STU &s2) { return s1.get_no() < s2.get_no(); } bool compare_by_score(const STU &s1, const STU &s2) { return s1.get_score() > s2.get_score(); } void output(std::ostream &out, std::vector<STU> &v) { for(auto &i: v) out << i << std::endl; } void save(string filename, std::vector<STU> &v) { using std::ofstream; ofstream out; out.open(filename); if(!out.is_open()) { std::cout << "fail to open file " << filename << std::endl; } output(out, v); out.close(); }
测试运行结果截图
3.实验任务3
程序源码
task3_1
#include <iostream> #include <fstream> #include <array> #define N 5 int main() { using namespace std; array<int, N> x {97, 98, 99, 100, 101}; ofstream out; out.open("data1.dat", ios::binary); if(!out.is_open()) { cout << "fail to open data1.dat\n"; return 1; } out.write(reinterpret_cast<char *>(&x), sizeof(x)); out.close(); }
测试运行结果截图
程序源码
task3_2
#include <iostream> #include <fstream> #include <array> #define N 5 int main() { using namespace std; array<int, N> x; ifstream in; in.open("data1.dat", ios::binary); if(!in.is_open()) { cout << "fail to open data1.dat\n"; return 1; } in.read(reinterpret_cast<char *>(&x), sizeof(x)); in.close(); for(auto i = 0; i < N; ++i) cout << x[i] << ", "; cout << "\b\b \n"; }#include <iostream> #include <fstream> #include <array> #define N 5 int main() { using namespace std; array<int, N> x; ifstream in; in.open("data1.dat", ios::binary); if(!in.is_open()) { cout << "fail to open data1.dat\n"; return 1; } in.read(reinterpret_cast<char *>(&x), sizeof(x)); in.close(); for(auto i = 0; i < N; ++i) cout << x[i] << ", "; cout << "\b\b \n"; }
测试运行结果截图
问题：对task3_2.cpp的代码稍做改动，把line8的数组类型从int类型修改成char类型，即： array<int,N> x; ----> 修改成: array<char, N> x; 其它不做任何改动，再次运行程序，观察运行结果是什么？尝试分析原因：为什么会是那样 的结果？
测试运行结果截图
原因分析：
char型占用1字节，int型占用4个字节。存储于data1.dat文件中时是用的char型，即a b c d e,原代码是int型读取，即97 98 99 100 101，而修改后以char型读取，读取时是一个字节个字节读取，所以会产生空格。
4.实验任务4
程序源码
task4.cpp
#include <iostream> #include "Vector.hpp" void test() { using namespace std; int n; cin >> n; Vector<double> x1(n); for(auto i = 0; i < n; ++i) x1.at(i) = i * 0.7; output(x1); Vector<int> x2(n, 42); Vector<int> x3(x2); output(x2); output(x3); x2.at(0) = 77; output(x2); x3[0] = 999; output(x3); } int main() { test(); }
Vector.hpp
#pragma once using namespace std; template <typename T> class Vector { private: int size; T *p; public: Vector(int n): size{n} {p = new T[n];}; Vector(int n, T x):size{n} { p = new T[n]; for (auto i = 0; i < n; i++) p[i] = x; }; Vector(const Vector<T> &y): size{y.size} { p = new T[size]; for (auto i = 0; i < y.size; i++) p[i] = y.p[i]; }; ~Vector()=default; int get_size() { return size; } T &at(int index){return p[index];} T &operator[](int index){return p[index];} friend void output(Vector &x) { int i; for (i = 0; i < x.size - 1; i++) { cout << x.p[i] << ", "; } cout << x.p[i] << endl; } };
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5.实验任务5
程序源码
task5
#include<iostream> #include <fstream> #include<iomanip> using namespace std; void output(std::ostream &out) { out<<" "; for(int i=97;i<123;i++) { out<<char(i)<<" "; } out<<endl; for(int i=1;i<=26;i++) { out<<setw(2)<<i; for(int j=i;j<i+26;j++) { out<<setw(2)<<char(65 + j % 26); } out<<endl; } } int main() { output(cout); ofstream out; out.open("cipher_key.txt"); if(!out.is_open()){ cout<<"fail to open file cipher_key.txt to write"<<endl; return 0; } output(out); out.close(); }
测试运行结果截图
