Update tree shaking example

website/src/playground/files/root/lib/Range.ts

@@ -157,8 +157,28 @@ export default class Range<T = never> implements Iterable<T> {
     return new Range(res());
   }
 
-  // TODO: Negative indexes
   at(n: number) {
+    if (n < 0) {
+      if (n === -1) {
+        return this.last();
+      }
+
+      let buf: T[] = [];
+      let len = -n;
+      let i = 0;
+
+      for (const x of this.iterable) {
+        buf[i % len] = x;
+        i++;
+      }
+
+      if (buf.length < len) {
+        return undefined;
+      }
+
+      return buf[i % len];
+    }
+
     let i = 0;
 
     for (const x of this.iterable) {
@@ -345,12 +365,11 @@ export default class Range<T = never> implements Iterable<T> {
       return new Range(iter());
     }
 
-    // TODO: `in` operator
-    if (hasKey(iter, Symbol.iterator)) {
+    if (Symbol.iterator in iter) {
       return new Range(iter);
     }
 
-    if (hasKey(iter, "next")) {
+    if ("next" in iter) {
       return Range.fromIterator(iter);
     }
 
@@ -388,13 +407,6 @@ export default class Range<T = never> implements Iterable<T> {
   }
 }
 
-function hasKey<Obj, K extends string | symbol>(
-  obj: unknown,
-  key: K,
-): obj is Obj & Record<K, unknown> {
-  return (obj as Record<K, unknown>)[key] !== undefined;
-}
-
 function never(x: never): never {
   throw new Error(`Unexpected value: ${x}`);
 }

website/src/playground/files/root/tutorial/treeShaking.ts

@@ -8,11 +8,11 @@
 // - `factorizeAsPowers`
 // - `BinaryTree`
 // - `NotNullish`
-// - `range`
+// - `Range`
 //
 // These definitions are not included, because the definitions exported by this
 // module do not need them. Omitting those unused definitions reduces the
-// bytecode for this module from 3,593 to 413 bytes.
+// bytecode for this module from 3,606 to 337 bytes.
 
 import { factorize } from "../lib/mod.ts";