Having trouble with variables in different functions for a calculator

[BryanTriana]

Hey guys I am new with C++(started 2 days ago) and I made two different projects for a simple calculator with very basic arithmetic expressions, the first project worked out fine because I made it all in one function but in the second one I tried going with various functions that would solve the expressions separately. I dont know what I am doing wrong, I think it might be something with the variables in between the main function and the others. Any help would be appreciated, thanks for reading.

 #include <iostream>

void addition(int a, int b)
{
    int add;
    add = a+b;
    std::cout << "The answer is " << std::endl << add << std::endl;
}
void subtraction(int a, int b)
{
    int sub;
    sub = a-b;
    std::cout << "The answer is " << std::endl << sub << std::endl;
}
void multiplication(int a, int b)
{
    int pro;
    pro = a*b;
    std::cout << "The answer is " << std::endl << pro <<std::endl;
}

void division(int a, int b)
{
    int div;
    div = a/b;
    std::cout << "The answer is " << std::endl << div << std::endl;
}


int main()
{
    int x;
    int a;
    int b;
    

    
    std::cout << "Choose the operation: +:1, -:2, *:3, /:4" << std::endl;
    std::cin >> x;
    std::cout << "Type the first number" << std::endl;
    std::cin >> a;
    std::cout << "Type the second number" << std::endl;
    std::cin >> b;
    
    
    
    if (x==1)
    {
        addition(a, b);
    }
    else if(x==2)
    {
        subtraction(a, b);
    }
    else if(x==3)
    {
        multiplication(a, b);
    }
    else if(x==4)
    {
        division(a, b);
    }
    

    return 0;
}

[caolan]

I compiled and executed. It seems to work fine.

[BryanTriana]

oh I think it was just an issue with something in xcode, the code seems to be fine.

[caolan]

if your code is doing weird, unexpected behaviour, try another compiler. There's an online one here: http://cpp.sh/.

Another troubleshooting method is to wipe out your .o, obj, or intermediate files and do a clean build.

[TheIdeasMan]

Hi,

Good work ! Not a bad effort for 2 days coding :+) I really like you are using std:: already :+D

However, a couple of problems with the division part.

First is that the types are int, integer division doesn't help you here. 2/4 is 0 and 25/13 is 1. So you could make the types double, that will solve that problem.

Next, it's always a good idea to check for division by zero before you do any division, otherwise you will have infinity. With a double this is a little more tricky, doubles are stored as binary fractions and are not exact, so we shouldn't compare them using ==, but we can use relational operators < and > and <= etc. Instead we see if it's absolute value is less than some precision value we choose. So it is "near enough" to zero for our purposes. Consider this snippet:

#include <cmath>

// ...
// ...

double a = 0.1; // really 0.09999999999997 say, or 0.10000000000002
double b = 1.0 - (10.0 * a) ;  // 3e-16 say if(b == 0.0) is false

const double PRECISION = 1e-4;  // 0.0001 change this to whatever suits you
bool IsNearToZero = false;

if (std::abs(b) < PRECISION) { 
   std::cout << "b is near enough to zero, using " << PRECISION << " as precision\n";
   IsNearToZero = true;
}

Good Luck !! And don't hesitate to ask questions :+)