Fix issue 6621 - add sliding window iterator

changelog/std-range-slides.dd

@@ -0,0 +1,33 @@
+`std.range.slides` (a fixed-size sliding window range) was added
+
+$(REF slides, std, range) allows to iterate a range in sliding windows:
+
+---
+import std.array : array;
+import std.algorithm.comparison : equal;
+
+assert([0, 1, 2, 3].slides(2).equal!equal(
+    [[0, 1], [1, 2], [2, 3]]
+));
+assert(5.iota.slides(3).equal!equal(
+    [[0, 1, 2], [1, 2, 3], [2, 3, 4]]
+));
+
+assert(iota(7).slides(2, 2).equal!equal([[0, 1], [2, 3], [4, 5]]));
+assert(iota(12).slides(2, 4).equal!equal([[0, 1], [4, 5], [8, 9]]));
+
+// set a custom stepsize (default 1)
+assert(6.iota.slides(1, 2).equal!equal(
+    [[0], [2], [4]]
+));
+
+assert(6.iota.slides(2, 4).equal!equal(
+    [[0, 1], [4, 5]]
+));
+
+// allow slides with less elements than the window size
+assert(3.iota.slides!(No.slidesWithLessElements)(4).empty);
+assert(3.iota.slides!(Yes.slidesWithLessElements)(4).equal!equal(
+    [[0, 1, 2]]
+));
+---