title: Swift error: use of unresolved identifier
body: <p>I'm learning Swift and iOS platform. I can't get this error to go away. I've searched and haven't found anything this basic. Help is appreciated. </p>
  
  <pre><code>import Foundation
  
  let num1 = 10
  let num2 = 5
  
  // declare the function answerResult, which takes and Int
  // and returns a string 
  
  func answerResult(answer : Int) -&gt;String
      if check(num1, num2, answer) {
         return "correct!" 
      }
      else {
         Return "I'm sorry, that's wrong."
      }
  }
  // Call the function with various numbers 
  answerResult(15)
  answerResult(0)
  answerResult(600)
  answerResult(5)
  </code></pre>
  
  <blockquote>
    <p>Playground execution failed:  /var/folders/c8/6w5z3zbx1477cqv1wcys2cd80000gn/T/./lldb/441/playground551 .swift :12:8: error: use of unresolved identifier 'check'
        if check(num1, num2, answer) {</p>
  </blockquote>