Returns Option<[T, List<T>]>

The optional of the pair of head and rest.

Examples

import { List, empty, unCons, singleton } from "./list.ts";
import * as Option from "./option.ts";
import { assertEquals } from "../deps.ts";

assertEquals(unCons(empty()), Option.none());
assertEquals(
    unCons(singleton(42)),
    Option.some([42, empty()] as [number, List<number>]),
);
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