6 replies to this topic

[Youbar]

Hi, I'm just starting out C++ and decided to have an attempt at making a calculator, probably very crude but it works. Anyway, I'm having a problem with the % operator. This is only a portion of my code, but you'll get the gist:

else if(response == 5) {
	   cout << "Remainder" << endl;
	   cout << "Enter first number: ";
	   cin >> fn;
	   cout << "Enter second number to divide and get remainder: ";
	   cin >> sn;
	   float ovrl = (fn % sn);
	   cout << ovrl << endl;
	   system("PAUSE");
	   goto startagain;
    }

The code returns this error:
invalid operands of types `float' and `float' to binary `operator%'

Full code here:

Spoiler

#include <iostream>
using namespace std;
float fn = 0;
float sn = 0;
float response = 0;
int yn = 0;
int main() {
    main:
    system("CLS");
    cout << "1. Division" << endl << "2. Multiplication" << endl << "3. Addition" << endl << "4. Subtraction" << endl << "5. Remainders" << endl;
    cin >> response;
    system("CLS");
    if(response == 1) {
	   cout << "Divison" << endl;
	   cout << "Enter first number: ";
	   cin >> fn;
	   cout << "Enter second number to divide: ";
	   cin >> sn;
	   float ovrl = (fn / sn);
	   cout << ovrl << endl;
	   system("PAUSE");
	   goto startagain;
    }
   
    else if(response == 2) {
	   cout << "Multiplication" << endl;
	   cout << "Enter first number: ";
	   cin >> fn;
	   cout << "Enter second number to multiply: ";
	   cin >> sn;
	   float ovrl = (fn * sn);
	   cout << ovrl << endl;
	   system("PAUSE");
	   goto startagain;
    }
   
    else if(response == 3) {
	   cout << "Addition" << endl;
	   cout << "Enter first number: ";
	   cin >> fn;
	   cout << "Enter second number to add: ";
	   cin >> sn;
	   float ovrl = (fn + sn);
	   cout << ovrl << endl;
	   system("PAUSE");
	   goto startagain;
    }
   
    else if(response == 4) {
	   cout << "Subtraction" << endl;
	   cout << "Enter first number: ";
	   cin >> fn;
	   cout << "Enter second number to subtract: ";
	   cin >> sn;
	   float ovrl = (fn - sn);
	   cout << ovrl << endl;
	   system("PAUSE");
	   goto startagain;
    }
   
    else if(response == 5) {
	   cout << "Remainder" << endl;
	   cout << "Enter first number: ";
	   cin >> fn;
	   cout << "Enter second number to divide and get remainder: ";
	   cin >> sn;
	   float ovrl = (fn % sn);
	   cout << ovrl << endl;
	   system("PAUSE");
	   goto startagain;
    }
   
    else {
	   goto main;
    }
	  
    startagain:
	   system("CLS");
	   cout << "Would you like to start again? (1 = Y / 2 = N)";
	   cin >> yn;
    if(yn == 1) {
	   goto main;
    }
   
    else if(yn == 2) {
	   exit(0);
    return 0;
    }
   
    else {
	   exit(0);
    }
}

[MrMonkeh]

I believe the modulus operator (%) only works with integer types. You'll have to convert fn and sn to integer if you want to use it.

Or...a quick search on google and I stumbled upon "fmod". Used like so:

fmod(5.5, 3.5) // takes numerator and denominator

Note: I've never used this function before, so no promises. Though I believe you need to include the math header file to use fmod.

[Youbar]

I don't understand the fmod function...but about the converting fn and sn to integers...wouldn't that remove the decimals and round it down?
e.g 1.2 % 5 would return 0.

Edited by Youbar, 12 October 2012 - 11:18 PM.

[RulerOfNothing]

fmod is simply a floating point version of the modulus operator. It takes two arguments (the numerator and denominator, in that order) and calculates the remainder like so:
remainder = numerator - quotient * denominator where quotient is an integer and the remainder is less than the denominator.
For example fmod(5.5,3.5) would return 2.

[Youbar]

Could you give me an example of how I would apply it to my script please? It's returning errors.
Thanks.

[L. Spiro]

float ovrl = fmodf(fn, sn);

…


L. Spiro

[Youbar]

Thanks, problem solved.