Missing something, works fine until the end

Code:

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#include

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Code:

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<iostream>
#include<string>
#include<iomanip>
usingnamespace std;
int main()
{
//declare variables
int dollars = 0;
int quarters = 0;
int dimes = 0;
int nickels = 0;
int pennies = 0;
int change = 0;
double amountDue = 0.0;
double amountPaid = 0.0;
double valChange = 0.0;
//enter input items
cout << "Enter the amount due: $";
cin >> amountDue;
cout << "Enter the amount the customer paid: $";
cin >> amountPaid;
//calculate
valChange = amountPaid - amountDue;
change = valChange * 100;
dollars = change / 100;
change = change - (dollars *100);
quarters = change / 25;
change = change - (quarters * 25);
dimes = change / 10;
change = change - (dimes * 10);
nickels = change / 5;
change = change - (nickels * 5);
pennies = change;
//display output
cout << "The change amount is: $" << valChange << endl;
cout << dollars << " dollars " << quarters << " quarters " << dimes << " dimes " << nickels << " nickels " << pennies << " pennies." << endl;
return 0;
}


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When I run this, it works fine until nickels and pennies. If there are no nickels, pennies calculate correctly. If there are nickels, it shows 0 pennies always.

What inputs are you supplying, what output is being produced, and how is it different from what you expect?

The only issues I can see are;

1) your inputs are floating point, so you would potentially being hit with precision concerns, as floating point types cannot precisely represent fractional powers of ten (0.1, 0.01, etc). This is an issue you may see, or you may not - depending on how lucky you get with errors cancelling out or reinforcing when subtracting. The calculation of nickels and pennies are most likely (of the ones you are doing) to be affected by such concerns.

2) Multiplying a floating point value by 100 may yield a value that overflows an int. If that happens, all bets are off with your code. The values where this can happen are compiler dependent (range of values that a float can represent or that an int can represent are implementation defined).

3) Another issue may arise if amountPaid is less than the amountDue. The results of expressions in your code for such inputs are compiler dependent, as it is implementation defined whether division of negative operands rounds up or down.

Those quibbles aside, I can't see how your code would produce incorrect numbers of nickels or pennies. Which leads me to guess that your expectations of "correct" behaviour differs from mine.

Quote:

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Originally Posted by grumpy

1) your inputs are floating point, so you would potentially being hit with precision concerns, as floating point types cannot precisely represent fractional powers of ten (0.1, 0.01, etc). This is an issue you may see, or you may not - depending on how lucky you get with errors cancelling out or reinforcing when subtracting. The calculation of nickels and pennies are most likely (of the ones you are doing) to be affected by such concerns.

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I ran the code and saw the above issue using MinGW GCC (Likely TDM build). Change of $1.43 resulted in 142 cents of change being calculated.

Tim S.

This is just a most basic program, the way it is described, the amountPaid will always be higher than the amountDue. Since I can't seem to get an int variable to use decimal places even with:
fixed << setprecision(2);
I figured going from double to int would cause precision errors, I just couldn't figure out how to do it.
If you want to see where the errors are, run it and answer:
amount due 76.34
amount paid 80.00

run it again and use:
amount due 76.14
amount paid 80.00

you will see what I mean.

Since you are trying to figure it out and failed; I will give you the fix to one of the issues.

Your code

Code:

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change = valChange * 100;

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IIRC, what I tried at school to fix this rounding bug.
Add 1/2 of a cent to the dollar amount this results in rounding the value up.

Code:

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change = (valChange) + 0.005 * 100;

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Tim S.

Instead of reading in a floating point value, try reading two integers separated by a full stop (where the second integer has, at most, two digits).

Even better, read input as a string (look up the function fgets() for a way to do that) and interpret the string as two integers separated by a full stop.

Quote:

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Originally Posted by grumpy

...look up the function fgets() for a way to do that...

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You mean std::getline, of course.