Enhanced iterator

examples/src/io/IOSamples.jetl

@@ -0,0 +1,62 @@
+interface class IAdder<in T> {
+  fun add(item : T) : Boolean
+}
+
+interface class ICloseable {
+  fun close()
+}
+
+abstract class JavaCloseableWrapper(closeable : java.io.Closeable) : ICloseable(closeable)
+
+fun streamCopy<T>(from : IIterable<T>, to : IAdder<T>) {
+  for (item in from) t.add(item)
+}
+
+class FileInput : IIterator<Byte>, JavaCloseableWrapper {
+  private val stream : InputStream
+  private var next : Int
+  private var nextUsed = false
+
+  this(file : File) : JavaCloseableWrapper(stream) { // implicitly throws IOException
+    stream = FileInputStream(file) // throws IOException
+  }
+
+  override fun next() {
+    if (!nextUsed) {
+      nextUsed = true
+      return next.as<Byte>
+    }
+    return
+  }
+  
+  override val hasNext {
+    get() { // implicitly throws IOException
+      if (nextUsed && next != -1) {
+        nextUsed = false
+        next = stream.read() // throws IOException
+      }
+      return next != -1        
+    }
+  }
+}
+
+class FileOutput throws IOException : IAdder<Byte>, JavaCloseableWrapper {
+  private val stream : OutputStream
+
+  this(file : File) : JavaCloseableWrapper(stream) {
+    stream = FileOutputStream(file)
+  }
+
+  override fun add(item : Byte) {
+    stream.write(item)
+  }
+}
+
+fun example() { // this does not rethrow, no appropriate parameters given
+
+  val f1 : File = ...
+  val f2 : File = ...
+
+  streamCopy(FileInput(f1), f2) // throws IOException, you must catch or rethrow explicitly
+
+}