Unprintable ASCII character found in Swift Source Code
<p><a href="https://i.stack.imgur.com/oSO4k.png" rel="noreferrer"><img src="https://i.stack.imgur.com/oSO4k.png" alt="enter image description here"></a></p>

<p>Hi, I am new to Swift language , can anyone explain why there is error with PI Symbol here.</p>

<pre><code>import Foundation

class CalculatorBrain
{

    private var accumulator = 0.0

    func setOperand(operand : Double) {
        accumulator = operand
    }

    func performOperations (symbol: String) {
        switch symbol {
            case "π" :
                accumulator = M_PI
            case "√" :
                accumulator = sqrt(accumulator)
            default : break
        }
    }

    var result : Double {
        get{
            return accumulator
        }
    }
}
</code></pre>

<p>reference
<a href="https://youtu.be/j50mPzDMWVQ?t=2303" rel="noreferrer">https://youtu.be/j50mPzDMWVQ?t=2303</a></p>