lesson9part2.txt

#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <cmath>

using namespace std;

unsigned int read(ifstream&, double&, double&, int&);
double futureValue(double&, double&, int&);
void display(ofstream&, double, double, int, double);


int main()
{
	string fileName, outputFile = "output.xls"; 
	double presentValue, interestRate, fValue;
	int numMonths;
	ifstream readFrom;
	ofstream outputTo;
	

	cout << "Enter input file name\n"; //prompt for filename
	getline(cin, fileName); //stores file name in fileName reference variable

	//opens "pipeline" to read in from fileName
	readFrom.open(fileName.c_str());
	//checks if fileName was properly opened
	if (!readFrom)
	{
		cout << "File \"" << fileName << "\" could not be opened\n"; //error message
		return 0; //program ends
	}

	//opens "pipeline" to output to "output.xls"
	outputTo.open(outputFile.c_str());
	//checks if "output.xls" was properly opened
	if (!outputTo)
	{
		readFrom.close(); //closes the readFrom file, fileName
		cout << "File \"output.xls\" could ont be opened\n"; //error message
		return 0; //program ends
	}

	outputTo << "Future Value\tPresent Value\tMonthly Interest\tMonths" << endl;

	unsigned int readVal;
	do
	{
		readVal = read(readFrom, presentValue, interestRate, numMonths); //sets readVal
		if (readVal == 2) //there were invalid values
		{
			fValue = futureValue(presentValue, interestRate, numMonths); //determines future value
			display(outputTo, presentValue, interestRate, numMonths, fValue); //displays error message
		}
		else if (readVal == 1) //values were read properly
		{
			fValue = futureValue(presentValue, interestRate, numMonths); //determines future value
			display(outputTo, presentValue, interestRate, numMonths, fValue); //outputs to outputFile
		}
	} while (readVal != 0);

	//close both our input and output files
	readFrom.close();
	outputTo.close();

	return 0;
}

//this will read in our data using our readFrom object, and alters the last three reference variables
unsigned int read(ifstream& readFrom, double& presentValue, double& interestRate, int& numMonths)
{
	int returnValue = 0; //sets default returnValue value for when the while loop doesn't enter because it's
	//either done reading data or it can't read data because the input file never opened
	while (readFrom >> presentValue >> interestRate >> numMonths)
	{
		//invalid data
		if (presentValue <= 0 || interestRate <= 0 || numMonths <= 0)
		{
			returnValue = 2;
			break;
		}
		
		//valid data
		else if (presentValue > 0 && interestRate > 0 && numMonths > 0)
		{
			returnValue = 1;
			break;
		}
	}
	interestRate = interestRate * .01; //converts percentage to decimal
	return returnValue;
}

//performs our calculation of our future Value (fValue)
double futureValue(double& presentValue, double& interestRate, int& numMonths)
{
	double fValue; 
	fValue = presentValue * pow((1 + interestRate), numMonths); 
	return fValue;
}


//responsible for output
void display(ofstream& outputTo, double presentValue, double interestRate, int numMonths, double futureValue)
{
	//outputs error message if data is invalid
	if (presentValue <= 0 || interestRate <= 0 || numMonths <= 0)
	{
		cout << fixed << setprecision(2) << presentValue << " ";
		cout << fixed << setprecision(3) << interestRate * 100 << " " << numMonths << endl;
		cout << "One or more of the above values are not greater than zero\n";
	}

	//outputs to our output.xls file
	else
	{
		outputTo << fixed << setprecision(2) << futureValue << "\t";
		outputTo << fixed << setprecision(2) << presentValue << "\t";
		outputTo << fixed << setprecision(3) << interestRate * 100 << "\t";
		outputTo << numMonths << endl;
	}

}