Calculator-App

A Simple Calculator App created by implementing binary operations in Swift.

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Division Issue

For Division.

            let lhs = currentValue.index(currentValue.startIndex, offsetBy: 0)
            let  rhs = currentValue.index(currentValue.startIndex, offsetBy: 2)
//Here LHS and RHS are just indices 0 and 2 
            let a = String(currentValue[lhs])
            let b = String(currentValue[rhs])
//a is just the character in position 0 and b is the character in position 2 (typecast as strings)
            let operand1 = Double(a)
            let operand2 = Double(b)
// operand 1 is double of the a. operand 2 is double of b
//This works if the two characters are numbers. But not if they are non-numeric. 
//If string is "1/3" then a is 1 and b is 3. So Double(a) and Double(b) are valid. 
//But if String is "12/3" then a is 1 and b is /. Double(b) is Double(/) which is invalid. So nil is //returned
            answer = operand1! / operand2!
//Here you are unwrapping an optional by using !. Operand1 and Operand2 must not be nil. 
//But they will be nil if either a or b are non-numeric and cannot be converted to Double.

Another error is that you can only divide with string of form "a/b" where a and b are two digits.
What about "aaa/b" "aa/bbb" etc etc.

The better solution is to use

let numberArray = currentValue.components(separatedBy: "/")
This returns an array of strings separated by "/". Then take the first two elements of the array and convert to double. Then divide.

  ```
    let a  = numberArray[0]
    let b  = numberArray[1]
          
    let operand1 = Double(a)
    let operand2 = Double(b)

    let answer: Double = operand1! / operand2!

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