End-Of-File question
End-Of-File question
- Subject: End-Of-File question
- From: Richard Rehl <email@hidden>
- Date: Fri, 21 Sep 2007 15:52:01 -0400
Newbie here with a question regarding a C++ project from "Accelerated
C++" by Koening/Moo. This is a program that's supposed to read a name
and a set of grades, terminated by entering end-of-file. It turns out
I need to enter it twice before the program actually does what it's
supposed to do - calculate and display the final grade. I'm assuming
the problem is somewhere in the read_hw function defined in
Student_info.cpp. Here's a sample output:
Please enter your first name, followed by your midterm and final
grades: richard
90
100
Please enter your homework grades, followed by end-of-file: 90
90
90
∂
Please enter your first name, followed by your midterm and final
grades: ∂
Please enter your homework grades, followed by end-of-file: richard 94
and here are the various files:
------------------------------------------------------------------------
------
main.cpp
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <ios>
#include <stdexcept>
#include <vector>
#include "grade.h"
#include "Student_info.h"
using std::cin;
using std::cout;
using std::endl;
using std::domain_error;
using std::max;
using std::setprecision;
using std::sort;
using std::streamsize;
using std::string;
using std::vector;
int main ()
{
vector<Student_info> students;
Student_info record;
string::size_type maxlen = 0;
//read and store 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)) {
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
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;
}
------------------------------------------------------------------------
----
Student_info.h
#ifndef GUARD_Student_info
#define GUARD_Student_info
#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(std::istream&, Student_info&);
std::istream& read_hw(std::istream&, std::vector<double>&);
#endif
------------------------------------------------------------------------
----
Student_info.cpp
#include "Student_info.h"
using std::istream;
using std::vector;
using std::cout;
bool compare(const Student_info& x, const Student_info& y)
{
return x.name < y.name;
}
istream& read(istream& is, Student_info& s)
{
cout << "Please enter your first name, followed by your midterm
and final grades: ";
is >> s.name >> s.midterm >> s.final;
cout << "Please enter your homework grades, followed by end-of-
file: ";
read_hw(is, s.homework);
return is;
}
istream& read_hw(istream& in, vector<double>& hw)
{
if(in)
{
hw.clear();
double x;
while(in >> x)
hw.push_back(x);
in.clear();
}
return in;
}
------------------------------------------------------------------------
----------------------
grade.h
#ifndef GUARD_grade_h
#define GUARD_grade_h
#include <vector>
#include "Student_info.h"
double grade(double, double, double);
double grade(double, double, const std::vector<double>&);
double grade(const Student_info&);
#endif
------------------------------------------------------------------------
------------------------
grade.cpp
#include "grade.h"
#include <stdexcept>
#include <vector>
#include "median.h"
#include "Student_info.h"
using std::domain_error;
using std::vector;
double grade(const Student_info& s)
{
if (s.homework.size() == 0)
throw domain_error("Student has done no homework");
return 0.2 * s.midterm + 0.4 * s.final + 0.4 * median(s.homework);
}
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