Generalize zip(..) to merge(..) { t1, t2 -> ... }, add merge for maps.

libraries/stdlib/test/collections/CollectionTest.kt

@@ -120,6 +120,20 @@ class CollectionTest {
         }
     }
 
+    test
+    fun merge() {
+        expect(listOf("ab", "bc", "cd")) {
+            listOf("a", "b", "c").merge(listOf("b", "c", "d")) { a, b -> a + b }
+        }
+    }
+
+    test
+    fun zip() {
+        expect(listOf("a" to "b", "b" to "c", "c" to "d")) {
+            listOf("a", "b", "c").zip(listOf("b", "c", "d"))
+        }
+    }
+
     test fun partition() {
         val data = arrayListOf("foo", "bar", "something", "xyz")
         val pair = data.partition { it.size == 3 }

libraries/stdlib/test/collections/MapTest.kt

@@ -53,7 +53,7 @@ class MapTest {
         assertEquals(map.size(), 1)
         assertEquals("James", map["name"])
     }
-    
+
     test fun iterate() {
         val map = TreeMap<String, String>()
         map["beverage"] = "beer"

libraries/stdlib/test/collections/StreamTest.kt

@@ -73,6 +73,13 @@ public class StreamTest {
         assertEquals("13, 21, 34, 55, 89, 144, 233, 377, 610, 987, ...", fibonacci().drop(3).drop(4).joinToString(limit = 10))
     }
 
+    test
+    fun merge() {
+        expect(listOf("ab", "bc", "cd")) {
+            streamOf("a", "b", "c").merge(streamOf("b", "c", "d")) { a, b -> a + b }.toList()
+        }
+    }
+
     test fun toStringJoinsNoMoreThanTheFirstTenElements() {
         assertEquals("0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...", fibonacci().joinToString(limit = 10))
         assertEquals("13, 21, 34, 55, 89, 144, 233, 377, 610, 987, ...", fibonacci().filter { it > 10 }.joinToString(limit = 10))