添加复用

base/reusing/studenti.cpp

@@ -0,0 +1,67 @@
+//
+// Created by zhuyijun on 2021/8/30.
+//
+
+#include "studenti.h"
+using std::ostream;
+using std::endl;
+using std::istream;
+using std::string;
+
+/**
+ * 求平均值
+ * @return double
+ */
+double Student::Average() const {
+    if (ArrayDb::size() > 0) {
+        return ArrayDb::sum() / ArrayDb::size();
+    }
+    return 0;
+}
+
+const std::string & Student::Name() const {
+    return (const string &) *this;
+}
+
+double &Student::operator[](int i) {
+    return ArrayDb::operator[](i);
+}
+
+double Student::operator[](int i) const {
+    return ArrayDb::operator[](i);
+}
+
+ostream &Student::arr_out(std::ostream &os) const {
+    int i;
+    int lim = ArrayDb::size();
+    if (lim > 0) {
+        for (i = 0; i < lim; ++i) {
+            os << ArrayDb::operator[](i) << " ";
+            if (i % 5 == 4) {
+                os << endl;
+            }
+        }
+        if (i % 5 != 0) {
+            os << endl;
+        }
+    } else {
+        os << " empty array ";
+    }
+    return os;
+}
+
+istream  & operator>>(istream & is,Student & stu){
+    is >> (string &) stu;
+    return is;
+}
+istream & getline(istream & is,Student & stu){
+    getline(is,(string &) stu);
+    return is;
+}
+
+ostream & operator<<(ostream & os,const Student & stu){
+    os <<"Scores for "<<(const string &) stu <<":\n";
+    stu.arr_out(os);
+    return os;
+}
+

base/reusing/studenti.h

@@ -0,0 +1,39 @@
+//
+// Created by zhuyijun on 2021/8/30.
+//
+
+#ifndef BASE_STUDENTI_H
+#define BASE_STUDENTI_H
+#include <iostream>
+#include <valarray>
+#include <string>
+/**
+ * 显示私有继承
+ */
+class Student: private std::string,private  std::valarray<double>{
+
+private:
+    typedef std::valarray<double> ArrayDb;
+    std::ostream & arr_out(std::ostream & os) const;
+
+public:
+    Student() :std::string("Null Student"),ArrayDb(){}
+    explicit Student(const std::string & s) :std::string(s),ArrayDb(){}
+    explicit Student(int n):std::string("Nully"),ArrayDb(n){}
+    Student(const std::string & s,int n) :std::string(s),ArrayDb(n){}
+    Student(const std::string & s,const ArrayDb & a) : std::string(s),ArrayDb(a){}
+    Student(const char * str,const double * pd,int n):std::string(str),ArrayDb(pd,n){}
+    ~Student(){};
+    double Average() const;
+    const std::string & Name() const;
+    double & operator[](int i);
+    double operator[](int i) const;
+
+    //友元
+    friend std::istream  & operator>>(std::istream & is,Student & stu);
+    friend std::istream  & getline(std::istream & is,Student & stu);
+    friend std::ostream & operator<<(std::ostream & os,const Student & stu);
+};
+
+
+#endif //BASE_STUDENTI_H

base/reusing/uses_stuci.cpp

@@ -0,0 +1,42 @@
+//
+// Created by zhuyijun on 2021/8/30.
+//
+
+#include <iostream>
+#include "studenti.h"
+using namespace std;
+void set(Student & sa,int n);
+const int pupils = 3;
+const int quizzes = 5;
+
+int main() {
+    Student ada[pupils] = {
+            Student{quizzes},Student{quizzes},Student{quizzes}
+    };
+    for (int i = 0; i < pupils; ++i) {
+        set(ada[i],quizzes);
+    }
+    cout <<"\nStudent List:\n";
+    for (int i = 0; i < pupils; ++i) {
+        cout <<ada[i].Name() << endl;
+    }
+    cout <<"\nResult:";
+    for (int i = 0; i < pupils; ++i) {
+        cout << endl <<ada[i];
+        cout <<"average: "<<ada[i].Average() << endl;
+    }
+    cout << "Done.\n";
+    return 0;
+}
+void set(Student & sa,int n){
+    cout <<"Please enter the student's name: ";
+    getline(cin,sa);
+    cout <<"Please enter " << n <<" quiz scores : \n";
+    for (int i = 0; i < n; ++i) {
+        cin >> sa[i];
+    }
+    while (cin.get() != '\n'){
+        continue;
+    }
+}
+