added a helper method for converting functions into iterators (which have all the various standard library APIs on them)

libraries/stdlib/src/Iterators.kt

@@ -1,6 +1,7 @@
 package kotlin
 
 import kotlin.support.AbstractIterator
+import kotlin.support.FunctionIterator
 
 import java.util.*
 import java.util.Iterator
@@ -77,3 +78,8 @@ inline fun <T, R> java.util.Iterator<T>.flatMap(transform: (T)-> java.util.Itera
     return flatMapTo<>(ArrayList<R>(), transform)
 }
 */
+
+/**
+ * Returns an iterator which invokes the function to calculate the next value on each iteration until the function returns null
+ */
+inline fun <T> iterate(nextFunction: () -> T?) : Iterator<T> = FunctionIterator(nextFunction)

libraries/stdlib/src/support/AbstractIterator.kt

@@ -70,4 +70,19 @@ abstract class AbstractIterator<T>: java.util.Iterator<T> {
     protected fun done() {
         state = State.Done
     }
+}
+
+/**
+ * An [[Iterator]] implementation which invokes a function to calculate the next value in the iteration
+ * until the function returns null
+ */
+class FunctionIterator<T>(val nextFn: () -> T?) : AbstractIterator<T>() {
+
+    override fun computeNext(): T? {
+        val next = (nextFn)()
+        if (next == null) {
+            done()
+        }
+        return next
+    }
 }

libraries/stdlib/test/iterators/FunctionIteratorTest.kt

@@ -0,0 +1,22 @@
+package iterators
+
+import kotlin.*
+import kotlin.test.*
+import kotlin.util.*
+
+import org.junit.Test
+
+class FunctionIteratorTest {
+
+    Test fun iterateOverFunction() {
+        var count = 3
+
+        val iter = iterate<Int> {
+            count--
+            if (count >= 0) count else null
+        }
+
+        val list = iter.toList()
+        assertEquals(arrayList(2, 1, 0), list)
+    }
+}