/*
 * Copyright (C) 2007-2016 Artima, Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Automatically generated Scala interpreter transcript from:
 *
 * Programming in Scala (Third Edition)
 * by Martin Odersky, Lex Spoon, Bill Venners
 *
 * http://booksites.artima.com/programming_in_scala_3ed
 */


scala>   // In file ChecksumAccumulator.scala
         class ChecksumAccumulator {
           private var sum = 0
           def add(b: Byte): Unit = { sum += b }
           def checksum(): Int = ~(sum & 0xFF) + 1
         }

defined class ChecksumAccumulator

scala>   // In file ChecksumAccumulator.scala
         import scala.collection.mutable
       
         object ChecksumAccumulator {
       
           private val cache = mutable.Map.empty[String, Int]
       
           def calculate(s: String): Int = 
             if (cache.contains(s))
               cache(s)
             else {
               val acc = new ChecksumAccumulator
               for (c <- s)
                 acc.add(c.toByte)
               val cs = acc.checksum()
               cache += (s -> cs)
               cs
             }
         }

import scala.collection.mutable
defined object ChecksumAccumulator
warning: previously defined class ChecksumAccumulator is not a companion to object ChecksumAccumulator.
Companions must be defined together; you may wish to use :paste mode for this.

scala> ChecksumAccumulator.calculate(
         ChecksumAccumulator.toString())  // Sum thyself!
res0: Int = -226

scala>   import ChecksumAccumulator.calculate
       
         object Summer {
           def main(args: Array[String]) = {
             for (arg <- args)
               println(arg + ": " + calculate(arg))
           }
         }

import ChecksumAccumulator.calculate
defined object Summer

scala> Summer.main(Array("of", "love"))
of: -213
love: -182