Divided Operation in Swift

Why can't I divide integers in swift?

The OP seems to know how the code has to look like but he is explicitly asking why it is not working the other way.

So, "explicitly" is part of the answer he is looking for: Apple writes inside the "Language Guide" in chapter "The Basics" -> "Integer and Floating-Point Conversion":

Conversions between integer and floating-point numeric types must be
made explicit

Divided operation in Swift

Swift has strict rules about the whitespace around operators. Divide '/' is a binary operator.

The important rules are:

• If an operator has whitespace around both sides or around neither
  side, it is treated as a binary operator. As an example, the +
  operator in a+b and a + b is treated as a binary operator.
• If an operator has whitespace on the left side only, it is treated as a
  prefix unary operator. As an example, the ++ operator in a ++b is
  treated as a prefix unary operator.
• If an operator has whitespace on
  the right side only, it is treated as a postfix unary operator. As an
  example, the ++ operator in a++ b is treated as a postfix unary
  operator.

That means that you need to add a space before the / or remove the space after it to indicate that it is a binary operator:

var rotation = Double(arc4random_uniform(50)) / (100.0 - 0.2)

If you want rotation to be a Float, you should use that instead of Double:

var rotation = Float(arc4random_uniform(50)) / (100.0 - 0.2)

There is no need to specify the type explicitly since it will be inferred from the value you are assigning to. Also, you do not need to explicitly construct your literals as a specific type as those will conform to the type you are using them with.

Divide two numbers and return fraction in swift

To get the quotient and remainder of a division, you can use the quotientAndRemainder(dividingBy:) function.

3.quotientAndRemainder(dividingBy: 6) // (quotient 0, remainder 3)

If you want to get the floating point result of a division, use the / operator on two floating point numbers.

Either do

let result = 3.0 / 6.0 // 0.5

or if your integers are coming from variables, do

let result = Double(3.0) / Double(6.0) // 0.5

Is the Swift divide / operator not working or have I missed something?

Your problem is here: 1/36. Both 1 and 36 are Ints. Try this:

var probabilitiesX = Array(repeating: 1.0 / 36.0, count: 36)

How to divide two numbers in swift using two variables?

1. Division operator is /, not \.

2. sum\numbers - um, what? Did you mean sum / numbers.count ?

Float divison and casting in Swift

First, you should use Double and not Float. Float gives you very limited precision. Why you would want 6 digits precision with Float when you could have 15 digits with Double is hard to understand.

Second, a compiler does exactly what you tell it.

Float (sum) / Float (numbers.count)

takes the integer "sum", takes the integer "numbers.count", converts both to Float and divides. Divison of Float gives a result in this case of 3.5.

Float (sum/numbers.count)

divides the integer "sum" by the integer "numbers.count". Division of integers gives an integer result, which is the integer quotient disregarding any remainder. 21 / 6 equals 3 with a remainder of 3. So the result of the division is 3, which you then convert to the Float 3.0.

Mathematical operations on CGPoint in Swift

It is not strictly meaningful to add two CGPoints. It's not completely wrong; it's just not meaningful because points are coordinates, not offsets. "Chicago + New York" is not a new location.

Generally you would offset a CGPoint using a CGVector, CGSize/NSSize, or a UIOffset. Those also don't have a + operator, but it would make more sense to add the operator to CGPoint+CGVector rather than two CGPoints.

But you're free to add it the way you did if it's particularly convenient.

How to execute multiplications and/or divisions in the right order?

If you only have the four operations +, -, x, and ÷, you can do this by keeping track of a pendingOperand and pendingOperation whenever you encounter a + or -.

Then compute the pending operation when you encounter another + or -, or at the end of the calculation. Note that + or - computes the pending operation, but then immediately starts a new one.

I have modified your function to take the stringNumbers, operators, and initial values as input so that it could be tested independently in a Playground.

func calculateTotal(stringNumbers: [String], operators: [String], initial: Double) -> Double {

    func performPendingOperation(operand: Double, operation: String, total: Double) -> Double {
        switch operation {
        case "+":
            return operand + total
        case "-":
            return operand - total
        default:
            return total
        }
    }

    var total = initial
    var pendingOperand = 0.0
    var pendingOperation = ""

    for (i, stringNumber) in stringNumbers.enumerated() {
        if let number = Double(stringNumber) {
            switch operators[i] {
            case "+":
                total = performPendingOperation(operand: pendingOperand, operation: pendingOperation, total: total)
                pendingOperand = total
                pendingOperation = "+"
                total = number
            case "-":
                total = performPendingOperation(operand: pendingOperand, operation: pendingOperation, total: total)
                pendingOperand = total
                pendingOperation = "-"
                total = number
            case "÷":
                total /= number
            case "×":
                total *= number
            default:
                break
            }
        }
    }

    // Perform final pending operation if needed
    total = performPendingOperation(operand: pendingOperand, operation: pendingOperation, total: total)

    // clear()
    return total
}

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Tests:

// 4 + 3    
calculateTotal(stringNumbers: ["3"], operators: ["+"], initial: 4)

7

// 4 × 3
calculateTotal(stringNumbers: ["3"], operators: ["×"], initial: 4)

12

// 2 + 2 × 4
calculateTotal(stringNumbers: ["2", "4"], operators: ["+", "×"], initial: 2)

10

// 2 × 2 + 4
calculateTotal(stringNumbers: ["2", "4"], operators: ["×", "+"], initial: 2)

8

// 17 - 2 × 3 + 10 + 7 ÷ 7
calculateTotal(stringNumbers: ["2", "3", "10", "7", "7"], operators: ["-", "×", "+", "+", "÷"], initial: 17)

22

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