perf(cancellations): use an Array instead of a linked list

Arrays have lower memory usage

benchmarks/README.md

@@ -22,7 +22,7 @@ Fastest is FIO
 
 ```bash
 node benchmarks/NestedMap.js
-Fluture x 8,518 ops/sec ±1.68% (77 runs sampled)
-FIO x 4,810 ops/sec ±1.56% (78 runs sampled)
+Fluture x 8,280 ops/sec ±3.43% (73 runs sampled)
+FIO x 5,838 ops/sec ±1.03% (80 runs sampled)
 Fastest is Fluture
 ```

src/cancellables/CancellationList.ts

@@ -1,31 +1,37 @@
 /**
  * Created by tushar on 2019-05-14
  */
-import {LinkedList, LinkedListNode} from 'dbl-linked-list-ds'
-
 import {ICancellable} from 'ts-scheduler'
 
+/**
+ * @ignore
+ */
+export type CancelId = number
+
 /**
  * Collection of cancellables
  * @ignore
  */
 export class CancellationList {
-  private readonly q = new LinkedList<ICancellable>()
+  private readonly q = new Array<ICancellable>()
 
   public cancel(): void {
-    let node = this.q.shift()
+    let node = this.q.pop()
     while (node !== undefined) {
       node.cancel()
-      node = this.q.shift()
+      node = this.q.pop()
     }
   }
 
-  public cancelId(node: LinkedListNode<ICancellable>): void {
-    node.value.cancel()
-    this.q.remove(node)
+  public cancelId(id: CancelId): void {
+    const node = this.q[id]
+    node.cancel()
+
+    this.q[id] = this.q[this.q.length - 1]
+    this.q.pop()
   }
 
-  public push(cancel: ICancellable): LinkedListNode<ICancellable> {
-    return this.q.add(cancel)
+  public push(cancel: ICancellable): CancelId {
+    return this.q.push(cancel) - 1
   }
 }

src/operators/Map.ts

@@ -15,15 +15,17 @@ class MapExecutor<R1, E1, A1, A2> implements IExecutable {
     private readonly res: (e: A2) => void,
     private readonly runtime: Runtime,
     private readonly cancellations: CancellationList
-  ) {}
+  ) {
+    this.onResolve = this.onResolve.bind(this)
+  }
 
   public execute(): void {
     this.cancellations.push(
       this.src.fork(this.env, this.rej, this.onResolve, this.runtime)
     )
   }
 
-  private readonly onResolve = (a: A1) => {
+  private onResolve(a: A1): void {
     this.res(this.ab(a))
   }
 }