title: Unprintable ASCII character found in Swift Source Code
body: <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>