/*
Marty Stepp, CSE 142, Spring 2010
Reads a file of temperatures and outputs the difference between each pair
of neighboring days.

Input file weather.txt:
16.2   23.5
   19.1 7.4  22.8

18.5  -1.8 14.9

Expected output:
16.2 to 23.5, change = 7.3
23.5 to 19.1, change = -4.4
19.1 to 7.4, change = -11.7
7.4 to 22.8, change = 15.4
22.8 to 18.5, change = -4.3
18.5 to -1.8, change = -20.3
-1.8 to 14.9, change = 16.7
*/

import java.io.*;     // for File
import java.util.*;

public class Temperatures {
    public static void main(String[] args) throws FileNotFoundException {
        Scanner input = new Scanner(new File("weather.txt"));

        // fencepost - pull out a "post" (reading a number)
        double prev = input.nextDouble();           // 16.2, 23.5, 19.1, ...

        while (input.hasNextDouble()) {
            // read a temperature from the file and process it
            double next = input.nextDouble();   // 23.5, 19.1, 7.4, ...
            double change = next - prev;
            System.out.println(prev + " to " + next + ", change = " + change);
            prev = next;                        // prev = 23.5
        }
    }
}