What does" invalid operands of types `int' and `double' to binary `operator%' "

[Morgan Huguelet]

Hello, Im a complete newbie to c++, so i would appriciate any help. I keep getting these errors in my program.
37 invalid operands of types `int' and `double' to binary `operator%'
i dont understand the problem, all of my varibles are ints.

//this program calculates the number of quarters,
// dimes and nickles and pennies are nessasary to
//generate the number of cents imputed
#include <iostream.h>
#include<string.h>

int main()
{
int toBeChanged, numberOfDimes, numberOfQuarters, numberOfNickels, numberOfPennies;
cout << " I will show you how many quarters, dimes, nickels, and \npennies needed to make the amount. How much money do you have?" << '\n';
cin >> toBeChanged;

if(toBeChanged >= .25)
{
numberOfQuarters = (int) (toBeChanged / .25);
toBeChanged = (toBeChanged % .25);
}

if(toBeChanged >= .1)
{
numberOfDimes = (int) (toBeChanged / .1);
toBeChanged = (toBeChanged % .1);
}

if(toBeChanged >= .05)
{
numberOfNickels = (int) (toBeChanged / .05);
toBeChanged = (toBeChanged % .05);
}

if(toBeChanged >= .01)
{
numberOfPennies = (int) (toBeChanged / .01);
toBeChanged = toBeChanged % .01;
}

cout << "For "<< toBeChanged << " you will need:"<<'\n';
cout <<numberOfQuarters<< " quarters,"<<'\n';
cout << numberOfDimes << " dimes,"<< '\n';
cout << numberOfNickels << " nickels,"<< '\n';
cout << numberOfPennies << " pennies."<< '\n';

system("pause");
return 0;
}

[codekiddy]

variables: toBeChanged, numberOfDimes, numberOfQuarters, numberOfNickels, numberOfPennies;

should be float I think, cos you're losing floating points.

[mjmckechnie]

I could be wrong... I am still learning C++, but I believe the '%' or 'modulus' only works on values of an 'int' data type... I actually worked through a problem like this a bit ago... let me see if I can't find the file and see how I did this...

[mjmckechnie]

it looks like i used a 'const' or 'constants' in my code... and where you have a decimal to represent change, i used the constant variable identifier...

const int HALFDOLLAR = 50; // a constant

change = change % HALFDOLLAR; // my assignment statement

[Gaminic]

mjmckechnie is correct. The modulo operator needs an int (>0, unless your head just doesn't hurt as much as you want it to) as argument.

[Morgan Huguelet]

@ codekiddy
yea they started out as floats, then doubles. But my % inst working with either.
i did try to convert it to float and i get
invalid operands of types `float' and `double' to binary `operator%'

@ mjmckechnie
thank you, any help is very appriciated.

[mjmckechnie]

@ mjmckechnie
thank you, any help is very appriciated.

Does that mean you still need help?

[Morgan Huguelet]

Actually the message waas suppose to nbe sent after you said you'd look. but yes i still need some guidence.
ive tried making my varibles const int as so

numberOfQuarters = (int) (toBeChanged / .25);
toBeChanged = (const int)(toBeChanged % .25);

and im still etting the same errors.

invalid operands of types `int' and `double' to binary `operator%'

[Peter87]

.25 is a double

[Morgan Huguelet]

Yes, but i cant use double with a %.

[Peter87]

Yes that is your problem.

If you want to do mod on floating point numbers you can use std::fmod. I have not studied your code in detail so I don't know if this is what you want.

[Morgan Huguelet]

So then i guess my question becomes
what do i use instead of a mod operation that will work the same with doubles?

[mjmckechnie]

	//Header file
#include <iostream>

using namespace std;

	//Named constants
const int HALFDOLLAR = 50;
const int QUARTER = 25;
const int DIME = 10;
const int NICKEL = 5;

int main()
{
		//Declare variable
	int change;

	cout << "Enter change in cents: ";		
	cin >> change;							
	cout << endl;

	cout << "The change you entered is " << change << endl;		

	cout << "The number of half-dollars to be returned is " << change / HALFDOLLAR << endl;		

	change = change % HALFDOLLAR;		

	cout << "The number of quarters to be returned is " << change / QUARTER << endl;		

	change = change % QUARTER;		

	cout << "The number of dimes to be returned is " << change / DIME << endl;		

	change = change % DIME;		

	cout << "The number of nickels to be returned is " << change / NICKEL << endl;		

	change = change % NICKEL;		

	cout << "The number of pennies to be returned is " << change << endl;		

	cout << endl << "Please press enter to exit the program...";

	cin.get();

	return 0;
}

generally, I believe that in learning to program we are supposed to look at other peoples code, and that will help us to learn. At the same time, I don't know if it is frowned upon to give you the whole answer or not here at this forum. But, here it is, this is the way I did it...

you can also write the assignment expression "change = change % NICKEL" like this, change "change %= NICKEL". It is just a simplified way of doing the same thing.

Hope it helps and that you learn something from it... :)

[Morgan Huguelet]

Thank you mjmckechnie,
it does help to look at other similar codes. yes this seems much more of a simple way of writing this program.
i rewrote my program a bit, but it still is kinda freaking out.
but at least i dont have the errors anymore

//this program calculates the number of quarters,
// dimes and nickles and pennies are nessasary to 
//generate the number of cents imputed
#include <iostream.h>
#include<string.h>

main() 
{
     double toBeChanged; 
     int numberOfDimes, numberOfQuarters, numberOfNickels, numberOfPennies;
     cout << " I will show you how many quarters, dimes, nickels, and \npennies needed to make the amount. \nHow much money do you have? (i.e. 1.25)" << '\n';
     cin >> toBeChanged;
     
cout << "For "<< toBeChanged << " you will need:"<<'\n';  
   
     toBeChanged = toBeChanged * 100;
          
      if(toBeChanged >= 25)
{
      numberOfQuarters =  (toBeChanged / 25);
      toBeChanged = (int)toBeChanged % 25;
}

      if(toBeChanged >= 10)
{
               numberOfDimes = (toBeChanged / 10);
               toBeChanged = (int)toBeChanged % 10;
}

               if(toBeChanged >= 5)
{
               numberOfNickels =  (toBeChanged / 5);
               toBeChanged = (int)toBeChanged % 5;
}

               if(toBeChanged >= 1)
{
               numberOfPennies = (toBeChanged  / 1);
               toBeChanged = (int)toBeChanged % 1;
}


cout << numberOfQuarters<< " quarters,"<<'\n';
cout << numberOfDimes << " dimes, "<< '\n';
cout << numberOfNickels << " nickels,"<< '\n';
cout << numberOfPennies << " pennies."<< '\n';

system("pause"); 
return 0;
}

so, it can get the quarters right, but then it messes up on the dimes and below.
any help?

[mjmckechnie]

So, if you do not initialize the variables and the change is say 785, it will only need the biggest value; which is quarters. But if you have 785.66, than all of the 'if' statements will work... this is why there is weird output... at least that is what I believe... I didn't spend to much time with it...

In other words, if the value of the input is a integer (say 785), then only the first 'if' statement executes...
and dimes, nickles, and pennies never get initialized...