DRAFT: implement sequence

src/sequence/containsAll.ts

@@ -0,0 +1,7 @@
+export function containsAll<T>(value: Iterable<T>, items: Iterable<T>): boolean {
+    const set = new Set(items);
+    for (const it of value) {
+        set.delete(it);
+    }
+    return set.size === 0;
+}