Just another update

Task/Non-continuous-subsequences/D/non-continuous-subsequences-3.d

@@ -0,0 +1,34 @@
+import std.stdio, std.array, std.range, std.concurrency;
+
+Generator!(T[]) ncsub(T)(in T[] seq) {
+    return new typeof(return)({
+        immutable n = seq.length;
+        auto S = new T[n];
+
+        foreach (immutable i; 1 .. 1 << n) {
+            uint lenS = 0;
+            bool nc = false;
+            foreach (immutable j; 0 .. n + 1) {
+                immutable k = i >> j;
+                if (k == 0) {
+                    if (nc)
+                        yield(S[0 .. lenS]);
+                    break;
+                } else if (k % 2) {
+                    S[lenS] = seq[j];
+                    lenS++;
+                } else if (lenS)
+                    nc = true;
+            }
+        }
+    });
+}
+
+void main() {
+    assert(24.iota.array.ncsub.walkLength == 16_776_915);
+
+    [1, 2, 3].ncsub.writeln;
+    [1, 2, 3, 4].ncsub.writeln;
+    foreach (const nc; [1, 2, 3, 4, 5].ncsub)
+        nc.writeln;
+}