15.05.2014

Author: 007kevin

Chapter04/4-6/ComputeStudentGrades_v3.cpp

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+#include <algorithm>
+#include <iomanip>      // defines setprecision manipulator
+#include <ios>          // defines streamsize
+#include <iostream>
+#include <stdexcept>
+#include <string>
+#include <vector>
+#include "grade.h"
+#include "Student_info.h"
+
+using std::cin;             using std::setprecision;
+using std::cout;            using std::sort;
+using std::domain_error;    using std::streamsize;
+using std::endl;            using std::string;
+using std::max;             using std::vector;
+
+int main(){
+    vector<Student_info> students;
+    Student_info record;          // temporary storage before pushing into students vector
+    string::size_type maxlen = 0; // to store length of the longest name for padding. 
+                                  //must be of string type to be used with max function
+
+    // read and store all the students data.
+    // Invariant: students contains all the student records read so far
+    while (read(cin, record)){
+        // find length of the longest name
+        maxlen = max(maxlen, record.name.size());
+        students.push_back(record);
+    }
+
+    // sort student records in alphabetical order
+    sort(students.begin(), students.end(), compare);
+
+    // output 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]); // calculate student's grade first in case domain_error is thrown
+            streamsize prec = cout.precision();
+            cout << setprecision(3) << final_grade
+                 << setprecision(prec); // restore precision
+        } catch (domain_error e){
+            cout << e.what();
+        }
+        cout << endl;
+    }
+
+    return 0;
+}
+

Chapter04/4-6/Student_info.cpp

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+// source file for Student_info-related functions
+#include "Student_info.h"
+
+using std::istream; using std::vector;
+
+bool compare(const Student_info& x, const Student_info& y){
+    return x.name < y.name;
+}
+
+istream& read(istream& is, Student_info& s){
+    // read and store the student's name and midterm and final exam grades
+    is >> s.name >> s.midterm >> s.final;
+
+    read_hw(is, s.homework); // read and store all the student's homework grades
+    return is;
+}
+
+// read homework grades from an input stream into a 'vector'
+istream& read_hw(istream& in, vector<double>& hw){
+    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;
+}

Chapter04/4-6/Student_info.h

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+#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;
+};
+// We will use these functions only if we are using the Student_info structure,
+// so it makes sense to package them together with the structure definition
+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

Chapter04/4-6/grade.cpp

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+#include <stdexcept>
+#include <vector>
+#include "grade.h"
+#include "median.h"
+#include "Student_info.h"
+
+using std::domain_error; using std::vector;
+
+// return calculated values
+double grade(double midterm, double final, double homework){
+    return 0.2 * midterm + 0.4 * final + 0.4 * homework;
+}
+
+// compute a student's overall grade from midterm and final exam grades
+// and vector of homework grades.
+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));
+}
+
+// compute grade from the Student_info reference to struct object
+double grade(const Student_info& s){
+    return grade(s.midterm, s.final, s.homework);
+}

Chapter04/4-6/grade.h

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+#ifndef GUARD_grade_h
+#define GUARD_grade_h
+
+// 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

Chapter04/4-6/median.cpp

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+// source file for the median function
+#include <algorithm>    // to get the declaration of sort
+#include <stdexcept>    // to get the declaration of domain_error
+#include <vector>       // to get the declaration of vector
+
+using std::domain_error; using std::sort; using std::vector;
+
+// compute the median of the vector<double>
+// note that calling this function copies the entire argument vector
+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] + vec[mid - 1]) / 2 : vec[mid];
+}

Chapter04/4-6/median.h

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+#ifndef GUARD_median_h
+#define GUARD_median_h
+
+#include <vector>
+double median(std::vector<double>);
+
+#endif