Exercise1.cpp

#include <algorithm>
#include <iomanip>
#include <iostream>
#include <stdexcept>
#include <string>
#include <vector>

using std::cin; using std::cout; using std::domain_error; using std::endl; using std::istream;
using std::ostream; using std::setprecision; using std::sort; using std::streamsize; using std::string; using std::vector;

double median(vector<double> vec) {
  typedef std::vector<double>::size_type vec_sz;
  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] + vec[mid-1]) / 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));
}

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;
}

int main() {
  cout << "Please enter your first name: ";
  string name;
  cin >> name;
  cout << "Hello, " << name << "!" << endl;

  cout << "Please enter your midterm and final exam grades: ";
  double midterm, final;
  cin >> midterm >> final;

  cout << "Enter all your homework grades, "
    "followed by end-of-file: ";

  vector<double> homework;


  read_hw(cin, homework);

  try {
    double final_grade = grade(midterm, final, homework);
    streamsize prec = cout.precision();
    cout << "Your final grade is " << setprecision(3)
     << final_grade << setprecision(prec) << endl;
  } catch (domain_error) {
    cout << endl << "You must enter your grades.  "
      "Please try again." << endl;
    return 1;
  }

  return 0;
}