Accelerated C++ 4 organizing programs and data

Student_info.h

#ifndef GUARD_Student_info#define GUARD_Student_info// Student_info.h header file#include <iostream>#include <string>#include <vector>struct Student_info{    std::string name;    double midterm, final;    std::vector<double>  homework;};bool compare(const Student_info&, const Student_info&);std::istream& read_hw(std::istream&, std::vector<double>&);std::istream& read(std::istream&, Student_info&);#endif

Student_info.cpp

// source file for Student_info-related functions#include <vector>#include <iostream>#include "Student_info.h"using std::cout;    using std::vector;  using std::istream;bool compare(const Student_info& x, const Student_info& y) {    return x.name < y.name;}istream& read_hw(istream& in, vector<double>& hw) {    // read and store the homework grades    cout << "Enter all your homework grades, "            "followd by end-of-file: ";    if (in) {        // get rid of previous contents        hw.clear();        // read homework grades        double x;        while (in >> x)            hw.push_back(x);        // clear the stream so that input will work for the next student        in.clear();    }    return in;}istream& read(istream& is, Student_info& s) {    // read and store the student's name and midterm and final exam grades    cout << "Please enter your first name, midterm and final exam grades: ";    is >> s.name >> s.midterm >> s.final;    read_hw(is, s.homework);    return is;}

grade.h

#ifndef GUARD_grade_h#define GUARD_grade_h// grade.h#include <vector>double median(std::vector<double>);double grade(double, double, double);double grade(double, double, const std::vector<double>&);double grade(const Student_info&);#endif

grade.cpp

// source file for the grade-ralated functons#include <vector>#include <stdexcept>#include "Student_info.h"#include "median.h"using std::vector;  using std::domain_error; using std::sort;double median(vector<double> vec) {    typedef vector<double>::size_type vec_sz;    vec_sz size = vec.size();    if (size == 0)        throw domain_error("median of an empty vector");    sort(vec.begin(), vec.end());    vec_sz mid = size / 2;    return size % 2 == 0 ? (vec[mid - 1] + vec[mid]) / 2 : vec[mid];}double grade(double midterm, double final, double homework) {    return 0.2 * midterm + 0.4 * final + 0.4 * homework;}double grade(double midterm, double final, const vector<double>& hw) {    if (hw.size() == 0)        throw domain_error("student has done no homework");    return grade(midterm, final, median(hw));}double grade(const Student_info& s) {    return grade(s.midterm, s.final, s.homework);}

main.cpp

#include <algorithm>#include <iomanip>  // setprecision#include <ios>      // streamsize   #include <iostream>#include <stdexcept>#include <string>#include "Student_info.h"#include "grade.h"using std::vector;          using std::sort;    using std::string;  using std::endl;using std::domain_error;    using std::cin;     using std::cout;    using std::max;using std::streamsize;      using std::setprecision;int main(){    vector<Student_info> students;    Student_info record;    string::size_type maxlen = 0;    // read and store all the students' data    // Invariant: students contains all the student records read so far    //            maxlen contains the length of the longest name in students    while (read(cin, record)) {        // find length of longest name        maxlen = max(maxlen, record.name.size());        students.push_back(record);    }    // alphabetize the student records    sort(students.begin(), students.end(), compare);    // write the names and grades    for (vector<Student_info>::size_type i = 0; i != students.size(); ++i){        // write the name, padded on the right to maxlen + 1 characters        cout << students[i].name << string(maxlen + 1 - students[i].name.size(), ' ');        // compute and write the grade        try {            double final_grade = grade(students[i]);            streamsize prec = cout.precision();            cout << setprecision(3) << final_grade << setprecision(prec);        } catch (domain_error e) {            cout << e.what();        }        cout << endl;    }    return 0;}