+shiffle

+List.binarySearch

docs/Array.md

@@ -0,0 +1,37 @@
+# Array
+
+It's an interface if the [Collection] that provides indexing access, like `array[3] = 0`.
+Array therefore implements [Iterable] too. The well known implementatino of the `Array` is
+[List].
+
+Array adds the following methods:
+
+## Binary search
+
+When applied to sorted arrays, binary search allow to quicly find an index of the element in the array, or where to insert it to keep order:
+
+    val coll = [1,2,3,4,5]
+    assertEquals( 2, coll.binarySearch(3) )
+    assertEquals( 0, coll.binarySearch(1) )
+    assertEquals( 4, coll.binarySearch(5) )
+
+    val src = (1..50).toList().shuffled()
+    val result = []
+    for( x in src ) {
+        val i = result.binarySearch(x)
+        assert( i < 0 )
+        result.insertAt(-i-1, x)
+    }
+    assertEquals( src.sorted(), result )
+    >>> void
+
+So `binarySearch(x)` returns:
+
+- index of `x`, a non-negative number
+- negative: `x` not found, but if inserted at position `-returnedValue-1` will leave array sorted.
+
+To pre-sort and array use `Iterable.sorted*` or in-place `List.sort*` families, see [List] and [Iterable] docs.
+
+[Collection]: Collection.md
+[Iterable]: Iterable.md
+[List]: List.md