#include <fstream>    // DOES fstream include iostream? NO;
#include <iostream>   // (comment this out, to see this!)
#include <cstdlib>    // (so can use exit function)
using namespace std;

// consider: what is DIFFERENT between this opening
//           comment block, and that for io1.cpp?
//           What is the SAME?

// Contract: void -> int
// Purpose: interactively find out how many rats there 
//          are, get their weights, and determine the total
//          of all of their weights. Print this total weight
//          in a message to the file "allRatWeights.txt" in
//          the directory from where this program is run.
//
// Examples: if, when prompted, the user enters 4,
//           then the user should be prompted to enter
//           4 rat weights; if the 4 weights entered
//           are 13.3, 5, 27.1, and 15.5, then it
//           should print to the file "allRatWeights.txt"
//           in the current directory:
// The total weight is 60.9
//
// by: Sharon M. Tuttle
// last modified: 10-28-03

int main ( )
{
    // local declarations
    double   weight, total = 0;
    int      num_rats;

    // we declare an ofstream variable, an output file 
    //    stream variable, giving it the name output_stream
    ofstream output_stream;

    // an output file stream needs to be OPENED in 
    //    order to write to it --- this open function 
    //    expects a single string parameter, representing 
    //    the name of the file where you want the output 
    //    to go
    // (why open it so soon? because why get the info 
    //    from the user, if will not be able to write
    //    to output file?)
    output_stream.open("allRatWeights.txt");
    if (output_stream.fail())
    {
        cout << "Could not open allRatWeights.txt for"
             << " output..." << endl;
        exit(1);
    }

    // if REACH here --- then successfully opened
    // output file;

    // how many rats are there?
    cout << "how many rats are being entered? ";
    cin >> num_rats;

    // get each rat's weight, accumulate sum of weights
    for (int i=0; i < num_rats; i++)
    {        
	cout << "Enter the next rat weight: ";
	cin >> weight;
	total += weight;
    }
    
    // report the sum of all the rats' weights, but to
    // the output file stream instead of to
    // cout! (Notice how, once you set it up, you treat
    // it like cout...)
    
    // (look how I can call an OS system call from
    //    C++ --- BUT THIS IS NOW 
    //    UNIX/LINUX/OS X-DEPENDENT!!)
    output_stream << system("date") << endl;
    output_stream <<  "The total weight is " << total 
                  << endl;

    // then, when you are done with it, you should 
    //    close your output file stream...
    output_stream.close();

    return 0;
}