Just another update

Task/Generator-Exponential/D/generator-exponential-5.d

@@ -0,0 +1,28 @@
+import std.stdio, std.range, std.algorithm, std.concurrency, std.bigint;
+
+auto powers(in uint m) pure nothrow @safe {
+    return 0.sequence!"n".map!(i => i.BigInt ^^ m);
+}
+
+auto filtered(R1, R2)(R1 r1, R2 r2) /*@safe*/
+if (isForwardRange!R1 && isForwardRange!R2 &&
+    is(ElementType!R1 == ElementType!R2)) {
+    return new Generator!(ElementType!R1)({
+        auto v = r1.front; r1.popFront;
+        auto f = r2.front; r2.popFront;
+
+        while (true) {
+            if (v > f) {
+                f = r2.front; r2.popFront;
+                continue;
+            } else if (v < f)
+                yield(v);
+            v = r1.front; r1.popFront;
+        }
+    });
+}
+
+void main() {
+    auto squares = 2.powers, cubes = 3.powers;
+    filtered(squares, cubes).drop(20).take(10).writeln;
+}