Converting data types

I am trying to convert a float to an int. I'm making a change calculator where the user enters an amount. I didn't want the result to be off because I've had results from floats come back 1 away from the correct answer. So this is what I have so far.

Code:

---

/*
  FILE:        Change_Calculator.cpp
  PROGRAMMER:  Stephen Michael Croy
  DATE:        01-07-09
  LAB:          1
 
  This program calculates the change from an amount input by the user
*/
 
#include <cstdlib>
#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
    //the following are the constants for this program
    const int HUNDRED  = 10000;
    const int FIFTY    = 5000;
    const int TWENTY    = 2000;
    const int TEN      = 1000;
    const int FIVE      = 500;
    const int ONE      = 100;
    const int QUARTER  = 25;
    const int DIME      = 10;
    const int NICKEL    = 5;
    const int PENNY    = 1;
   
    //entered by user
    float amount;
    float payment;
    int intAmount;
    int intPayment;
    int total;
   
    cout << "Enter the amount of purchase: "; //Prompt for data
    cin >> amount; //read information from user into amount
   
    cout << "Enter payment toward purchase: ";
    cin >> payment; //read information from user into payment
   
    intAmount = amount * 100;
    intPayment = payment * 100;
   
    if (intAmount > intPayment)
      total = intAmount - intPayment;
      cout << total;
     
   
   
   
    system("PAUSE");
    return EXIT_SUCCESS;
}

---

I know the program isn't finished, I'm just hung up on this conversion.

So if you multiplied the amount and payment by 100, then you must divide the total by 100.
Also check out alternatives to system("pause"): http://apps.sourceforge.net/mediawik...=Pause_console

In order to avoid issues with truncation, a quick fix would be

Code:

---

    intAmount = amount * 100 + 0.5;
    intPayment = payment * 100 + 0.5;

---

The reason is that a float * 100 may end up just a tiny bit below the actual value due to approximate nature of floating point values, e.g 0.11 * 100 = 10.999996 and if you truncate it to int it will become 10.

However, I think normally you should just avoid floating point values where the approximation errors are unacceptable. E.g take the input as a string, parse it to two integers, multiply the first part by 100 and add the second part as needed (avoid errors where user enters 10.5 or 2.345).

Code:

---

    const int HUNDRED  = 10000;
    const int FIFTY    = 5000;
    const int TWENTY    = 2000;
    const int TEN      = 1000;
    const int FIVE      = 500;
    const int ONE      = 100;
    const int QUARTER  = 25;
    const int DIME      = 10;
    const int NICKEL    = 5;
    const int PENNY    = 1;

---

When you continue you'll probably find that this will be better off as an array (perhaps even a map of numeric values and string names).

Thank you for the suggestions. Although they were helpful, they weren't exactly what I was looking for. I just want to know how to convert the float into an int.

But you have been given suggestions on how to do it...
Floats are not exact either, so there may be precision errors when converting to/from floats.

Elysia is right. There are a few ways to do it but the results may not be exactly what you want. You can use bit the bit-wise operators to get values. There is a lot of info on the net about that. Other than that you can:

float x = 5.2;
static_cast<int>(x);

that will just give you 5 because it is going to drop everything after the decimal. But it will convert the float into an int.

There are ways to store money as integers by storing the values as BCDs.