Returns Option<T>

The first element of list if exists.

Examples

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

assertEquals(head(empty()), Option.none());
assertEquals(head(fromString("hoge")), Option.some("h"));

const list = singleton(42);
assertEquals(head(list), Option.some(42));
assertEquals(head(list.rest()), Option.none());
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