DRAFT: implement sequence

src/sequence/first.ts

@@ -0,0 +1,8 @@
+import {error} from "../util/error.js";
+
+export function first<T>(value: Iterable<T>, predicate?: (it: T) => boolean): T {
+    for (const it of value) {
+        if (!predicate || predicate(it)) return it;
+    }
+    error();
+}