title: 'not found: type' error
body: <p>I'm reading 'Programming in scala' and in one of the example when I try to compile it in Eclipse I receive error : 'not found: type ChecksumAccumulator' The type is declared as below. Is the code below correct ?</p>
  
  <pre><code>import scala.collection.mutable.Map
  
  object ChecksumAccumulator {
  
    private val cache = Map[String, Int]()
  
    def calculate(s: String): Int = 
      if(cache.contains(s))
        cache(s)
      else {
        val acc = new ChecksumAccumulator
        for(c &lt;- s)
          acc.add(c.toBye)
        val cs = acc.checksum()
        cache += (s -&gt; cs)
        cs
      }
  }
  </code></pre>