windowed function: add default parameters, drop or keep partial windows, KEEP-11

Make step default to 1.
Add partialWindows boolean parameter defaulting to false to control
whether to keep partial windows in the end.

libraries/stdlib/test/collections/IterableTests.kt

@@ -167,23 +167,36 @@ abstract class OrderedIterableTests<T : Iterable<String>>(createFrom: (Array<out
         val size = 7
         val data = createFrom(Array(size) { "$it" })
         val result = data.windowed(4, 2)
+        assertEquals(listOf(
+                listOf("0", "1", "2", "3"),
+                listOf("2", "3", "4", "5")
+        ), result)
+
+        val resultPartial = data.windowed(4, 2, partialWindows = true)
         assertEquals(listOf(
                 listOf("0", "1", "2", "3"),
                 listOf("2", "3", "4", "5"),
                 listOf("4", "5", "6"),
                 listOf("6")
-        ), result)
+        ), resultPartial)
+
 
         val result2 = data.windowed(2, 3) { it.joinToString("") }
-        assertEquals(listOf("01", "34", "6"), result2)
+        assertEquals(listOf("01", "34"), result2)
 
-        assertEquals(data.chunked(2), data.windowed(2, 2))
+        val result2partial = data.windowed(2, 3, partialWindows = true) { it.joinToString("") }
+        assertEquals(listOf("01", "34", "6"), result2partial)
+
+        assertEquals(data.chunked(2), data.windowed(2, 2, partialWindows = true))
 
         assertEquals(data.take(2), data.windowed(2, size).single())
         assertEquals(data.take(3), data.windowed(3, size + 3).single())
 
-        val result3 = data.windowed(size, 1)
-        result3.forEachIndexed { index, window ->
+        assertEquals(data.toList(), data.windowed(size, 1).single())
+        assertTrue(data.windowed(size + 1, 1).isEmpty())
+
+        val result3partial = data.windowed(size, 1, partialWindows = true)
+        result3partial.forEachIndexed { index, window ->
             assertEquals(size - index, window.size, "size of window#$index")
         }
 

libraries/stdlib/test/collections/SequenceTest.kt

@@ -259,23 +259,36 @@ public class SequenceTest {
         val seq = infiniteSeq.take(7)
 
         val result1 = seq.windowed(4, 2)
+        assertEquals(listOf(
+                listOf(0, 1, 2, 3),
+                listOf(2, 3, 4, 5)
+        ), result1.toList())
+
+        val result1partial = seq.windowed(4, 2, partialWindows = true)
         assertEquals(listOf(
                 listOf(0, 1, 2, 3),
                 listOf(2, 3, 4, 5),
                 listOf(4, 5, 6),
                 listOf(6)
-        ), result1.toList())
+        ), result1partial.toList())
 
         val result2 = seq.windowed(2, 3) { it.joinToString("") }
-        assertEquals(listOf("01", "34", "6"), result2.toList())
+        assertEquals(listOf("01", "34"), result2.toList())
 
-        assertEquals(seq.chunked(2).toList(), seq.windowed(2, 2).toList())
+        val result2partial = seq.windowed(2, 3, partialWindows = true) { it.joinToString("") }
+        assertEquals(listOf("01", "34", "6"), result2partial.toList())
+
+        assertEquals(seq.chunked(2).toList(), seq.windowed(2, 2, partialWindows = true).toList())
 
         assertEquals(seq.take(2).toList(), seq.windowed(2, size).single())
         assertEquals(seq.take(3).toList(), seq.windowed(3, size + 3).single())
 
-        val result3 = seq.windowed(size, 1)
-        result3.forEachIndexed { index, window ->
+
+        assertEquals(seq.toList(), seq.windowed(size, 1).single())
+        assertTrue(seq.windowed(size + 1, 1).none())
+
+        val result3partial = seq.windowed(size, 1, partialWindows = true)
+        result3partial.forEachIndexed { index, window ->
             assertEquals(size - index, window.size, "size of window#$index")
         }
 

libraries/stdlib/test/text/StringTest.kt

@@ -884,18 +884,27 @@ class StringTest {
         val size = 7
         val data = arg1("abcdefg")
         val result = data.windowed(4, 2)
-        assertEquals(listOf("abcd", "cdef", "efg", "g"), result)
+        assertEquals(listOf("abcd", "cdef"), result)
+
+        val resultPartial = data.windowed(4, 2, partialWindows = true)
+        assertEquals(listOf("abcd", "cdef", "efg", "g"), resultPartial)
 
         val result2 = data.windowed(2, 3) { it.reversed().toString() }
-        assertEquals(listOf("ba", "ed", "g"), result2)
+        assertEquals(listOf("ba", "ed"), result2)
+        val result2partial = data.windowed(2, 3, partialWindows = true) { it.reversed().toString() }
+        assertEquals(listOf("ba", "ed", "g"), result2partial)
 
-        assertEquals(data.chunked(2), data.windowed(2, 2))
+        assertEquals(data.chunked(2), data.windowed(2, 2, partialWindows = true))
 
         assertEquals(data.take(2), data.windowed(2, size).single())
         assertEquals(data.take(3), data.windowed(3, size + 3).single())
 
-        val result3 = data.windowed(size, 1)
-        result3.forEachIndexed { index, window ->
+
+        assertEquals(data.toString(), data.windowed(size, 1).single())
+        assertTrue(data.windowed(size + 1, 1).isEmpty())
+
+        val result3partial = data.windowed(size, 1, partialWindows = true)
+        result3partial.forEachIndexed { index, window ->
             assertEquals(size - index, window.length, "size of window#$index")
         }
 
@@ -907,8 +916,11 @@ class StringTest {
         }
 
         for (window in 1..size + 1) {
-            for (step in 1..size + 1)
-            compare(data.windowed(window, step).iterator(), data.windowedSequence(window, step).iterator()) { iteratorBehavior() }
+            for (step in 1..size + 1) {
+                compare(data.windowed(window, step).iterator(), data.windowedSequence(window, step).iterator()) { iteratorBehavior() }
+                compare(data.windowed(window, step, partialWindows = true).iterator(),
+                        data.windowedSequence(window, step, partialWindows = true).iterator()) { iteratorBehavior() }
+            }
         }
     }