type StudentId = number | string;

interface Course {
  title: string;
  finished: boolean;
}

interface Student {
  id: StudentId;
  name: string;
  age?: number;
  courses: Course[];
}

function pickFirst<T>(list: T[]): T {
  return list[0];
}

function formatStudent(student: Student): string {
  // 返回一段摘要文字
  return `学号：${student.id}
  姓名：${student.name}
  年龄：${student.age?.toFixed()}`;
}

const student: Student = {
  id: "stu-1",
  name: "林晨",
  courses: [
    { title: "基本类型", finished: true },
    { title: "接口", finished: false },
  ],
};

console.log(formatStudent(student), pickFirst(student.courses));

// 任务：
// 1. 实现 formatStudent
// 2. 用 pickFirst 取第一门课程
// 3. 输出摘要和第一门课程