User-0.swift

// Pure function
func sum(_ num1: Int, _ num2: int) -> Int {
    return num1 + num2
}


// Impure function
var accumulated = 0
func add(_ num: Int) -> Int {
    accumulated = num + accumulated
    return accumulated
}

// Pure class
struct Accumulator {
    var value: Int

    // Still impure function
    func add(_ num: Int) -> Int {
        value = num + value
        return value
    }
}