Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 10 Exercise 3
Using std_lib_facilities.h by Bjarne Stroustrup.
[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PPP
// Chapter 10 Exercise 3
#include "std_lib_facilities.h"
struct Reading {
int hour;
double temperature;
};
struct Stats {
double mean;
double median;
};
ostream& operator<<(ostream& os, Stats _stats) {
os << "mean: " << _stats.mean << " median: " << _stats.median << endl;
return os;
}
vector<Reading> temps;
string iname = "output/raw_temps.txt";
ifstream ist(iname);
void read_file(vector<Reading>& _temps, string _file_name) {
if (!ist) { error("Could not open file", _file_name); }
cout << "Reading file." << endl;
int h;
double t;
while (ist >> h >> t) {
temps.push_back(Reading{ h,t });
}
cout << "Done!" << endl;
}
Stats calculate_stats(vector<Reading>& _temps) {
cout << "Calculating mean and median." << endl;
double sum = 0;
double mean;
double median;
int size = int(_temps.size());
for (int i = 0; i < size; i++) {
sum += _temps[i].temperature;
}
mean = sum / size;
vector<double> sorted_temps;
for (int i = 0; i < size; i++) {
sorted_temps.push_back(_temps[i].temperature);
}
sort(sorted_temps);
if (size % 2 == 0) {
median = (sorted_temps[size / 2] + sorted_temps[(size / 2) – 1]) / 2;
}
else {
median = sorted_temps[(size – 1) / 2];
}
return Stats{ mean, median };
}
int main()
try
{
read_file(temps, iname);
cout << calculate_stats(temps);
keep_window_open();
}
catch (runtime_error e) {
cout << e.what() << endl;
keep_window_open();
}
catch (…) {
cout << "Exiting" << endl;
keep_window_open();
}
[/code]
Output: Reading file. Done! Calculating mean and median. mean: 47.64 median: 48.5 Please enter a character to exit
Input-File raw_temps.txt: 0 78 1 14 2 1 3 15 4 72 5 20 6 65 7 54 8 49 9 67 10 48 11 73 12 67 13 49 14 20 15 42 16 76 17 38 18 36 19 40 20 15 21 87 22 16 23 51 0 34 1 63 2 37 3 48 4 79 5 41 6 60 7 21 8 15 9 51 10 1 11 41 12 84 13 13 14 79 15 38 16 0 17 16 18 86 19 88 20 76 21 50 22 73 23 77 0 74 1 44