/******************************************************************
CSCI 240         Assignment 6 Part 1     Fall 2025

Programmer:

Section:

Date Due:

Purpose:   This program uses functions to test the effects of
           rounding to the nearest $10.

           It is an exercise in learning to call functions.
******************************************************************/

#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

//Function Prototypes

double getExact();
double roundAmount( double );
double calcAverage( double, int );
double calcStdDev( double, double, int );
double calcDiff( double, double );


int main()
{
double exactAmt,                  /* exact dollar amount                   */
       roundedAmt,                /* amount rounded to nearest $10         */
       exactSum = 0.0,            /* sum of exact dollar amounts           */
       exactSumSquared = 0.0,     /* sum of squared exact dollar amounts   */
       roundedSum = 0.0,          /* sum of rounded dollar amounts         */
       roundedSumSquared = 0.0,   /* sum of squared rounded dollar amount  */
       exactAvg,                  /* average of exact dollar amounts       */
       roundedAvg,                /* average of rounded dollar amounts     */
       exactSD,                   /* standard deviation of exact amounts   */
       roundedSD,                 /* standard deviation of rounded amounts */
       percentDiff;               /* % difference between exact & rounded  */

int cnt = 0;                      /* number of dollar amounts entered      */



//*********************************************************************
//*
//* Fill In The Blank 1:
//*
//* Get the first EXACT dollar amount from the user by calling the getExact
//* function. The value returned from the function should be saved in
//* the exactAmt variable.
//*
//*********************************************************************





//While the user is still entering dollar amounts

while (exactAmt != 0.00)
  {

  //*********************************************************************
  //*
  //* Fill In The Blank 2:
  //*
  //* Round the user's EXACT dollar amount to the nearest ten dollar
  //* amount by calling the roundAmount function. The value returned from
  //* the function should be saved in the roundedAmt variable.
  //*
  //*********************************************************************





  //Calculate sums for the EXACT and ROUNDED amounts

  exactSum += exactAmt;
  exactSumSquared += (exactAmt * exactAmt);

  roundedSum += roundedAmt;
  roundedSumSquared += (roundedAmt * roundedAmt);


  //Increment the count of dollar amounts entered

  cnt++;


  //*********************************************************************
  //*
  //* Fill In The Blank 3:
  //*
  //* Get the next EXACT dollar amount from the user by calling the getExact
  //* function. The value returned from the function should be saved in
  //* the exactAmt variable.
  //*
  //*********************************************************************




  } //closing curly brace for the while loop


//*********************************************************************
//*
//* Fill In The Blank 4:
//*
//* Using the exactSum and cnt variables, calculate the average for the
//* EXACT dollar amounts by calling the calcAverage function. The value
//* returned from the function should be saved in the exactAvg variable.
//*
//*********************************************************************





//*********************************************************************
//*
//* Fill In The Blank 5:
//*
//* Using the roundedSum and cnt variables, calculate the average for the
//* ROUNDED dollar amounts by calling the calcAverage function. The value
//* returned from the function should be saved in the roundedAvg variable.
//*
//*********************************************************************





//*********************************************************************
//*
//* Fill In The Blank 6:
//*
//* Using the exactSum, exactSumSquared and cnt variables, calculate the
//* standard deviation of the EXACT dollar amounts by calling the calcStdDev
//* function. The value returned from the function should be saved in
//* the exactSD variable.
//*
//*********************************************************************





//*********************************************************************
//*
//* Fill In The Blank 7:
//*
//* Using the roundedSum, roundedSumSquared and cnt variables, calculate
//* the standard deviation of the ROUNDED dollar amounts by calling the
//* calcStdDev function. The value returned from the function should be
//* saved in the roundedSD variable.
//*
//*********************************************************************





//Display the calculated sums, averages and standard deviations for both
//the exact and rounded values or an error message if the average or
//standard deviation could not be calculated.

cout << fixed << setprecision(2);

cout << endl << "Calculation         Exact          Rounded"
     << endl << "------------------------------------------"
     << endl << "Sum:" << setw(21) << exactSum << setw(17) << roundedSum;
  
if ( exactAvg == -1 )  // could also add || roundAvg == -1
  {
  cout << endl << "Average:   *** could not be calculated ***";
  }
else
  {
  cout << endl << "Average:" << setw(17) << exactAvg << setw(17) << roundedAvg;
  }
  
if ( exactSD == -1 )  // could also add || roundedSD == -1
  {
  cout << endl << "Std Dev:   *** could not be calculated ***";
  }
else
  {
  cout << endl << "Std Dev:" << setw(17) << exactSD << setw(17) << roundedSD;
  }



//Calculate the percent difference and display the results if dollar
//amounts have been entered. Otherwise, display an error message

if (cnt > 0)
  {
  //*********************************************************************
  //*
  //* Fill In The Blank 8:
  //*
  //* Using the exactSum and roundedSum variables, calculate the percent
  //* difference between the EXACT and ROUNDED sums by calling the
  //* calcDiff function. The value returned from the function should be
  //* saved in the percentDiff variable.
  //*
  //*********************************************************************





  cout << endl << endl << "The difference is " << percentDiff << ". Rounding is ";
  
  if (percentDiff < 2.0)
    {
    cout << "acceptable";
    }
  else 
    {
    cout << "unacceptable";
    }
  }
else
  {
  cout << endl << endl << "The difference cannot be calculated";
  }

cout << endl;

return 0;
}/* end of main */


/******************************************************************
* 
* getExact
* 
* This function gets an exact dollar amount from the user. It
* makes sure the value is 0 or positive.
* 
* @param   None
* 
* @return  The exact dollar amount - a value that is either 0 or
*          positive
* 
******************************************************************/

double getExact()
{
//Create a variable to hold the amount that is entered by the user
double amount;


//Get a positive dollar amount (or 0) from the user
cout << "Enter a positive dollar amount or 0 to quit: ";
cin >> amount;

//While the user's amount is invalid, get a new one
while ( amount < 0 )
  {
  //Display an error message about an invalid amount and get a new one
  cout << "Error: amount must be greater than or equal to 0. Try again: ";
  cin >> amount;
  }//end of while


//Return the valid dollar amount

return amount;
}


/******************************************************************
* 
* roundAmount
* 
* This function rounds a value to the nearest $10 dollar amount
* 
* @param amount   the value to be rounded
* 
* @return    The rounded amount
* 
******************************************************************/

double roundAmount( double amount )
{
//Calculate the amount rounded to the nearest $10 amount and
//return the result

return ((int) ((amount + 5) / 10)) * 10;
}


/******************************************************************
* 
* calcAverage
* 
* This function calculates an average.
* 
* @param sum     the sum of all of the values
* @param count   the number of values
* 
* @return  The calculated average or -1 if the average cannot be
*          calculated
* 
******************************************************************/

double calcAverage(double sum, int count)
{
//If the count is 0 or negative, return the error code of -1;
//Otherwise, calculate the average and return the result

if( count < 1 )
  {
  return -1;
  }
else
  {
  return sum / count;
  }
}


/******************************************************************
* 
* calcStdDev
* 
* This function calculates a standard deviation.
* 
* @param sum             the sum of all of the values
* @param sumOfSquares    the sum of all of the squared values
* @param count           the number of values
* 
* @return   The calculated standard deviation or -1 if the standard
*           deviation cannot be calculated
* 
******************************************************************/

double calcStdDev( double sum, double sumOfSquares, int count )
{
//If the count is less than or equal to 1, return the error code of -1;
//Otherwise, calculate the standard deviation and return the result

if( count <= 1 )
  {
  return -1;
  }
else
  {
  return sqrt ((sumOfSquares - (sum * sum / count)) / (count - 1));
  }
}


/******************************************************************
* 
* calcDiff
* 
* This function calculates a percent difference
* 
* @param exactSum - the sum of all of the EXACT values
* @param roundedSum - the sum of all of the ROUNDED values
* 
* @return    The calculated percent difference
* 
* @note  The fabs function is used to calculate an absolute value
* 
******************************************************************/

double calcDiff( double exactSum, double roundedSum )
{
//Calculate the percent difference and return the result

return ((fabs(exactSum - roundedSum)) / exactSum) * 100;
}