Belajar Dart

void main() {
  print("Halo, Dart!");
  print("Nanti belajar");
}

void main() {
  // komentar satu baris
  print("Halo dari Dart!");

  /// doc comment — untuk dokumentasi API
  String nama = "Ari";
  int umur = 17;
  print("$nama berumur ${umur + 1} tahun depan");
}

void main() {
  final nama = "Ari";
  int umur = 17;
  print("$nama $umur");
}

void main() {
  var nama = "Ari";       // String, bisa re-assign
  final umur = 17;         // int, tidak bisa re-assign
  const pi = 3.14159;      // compile-time constant

  nama = "Budi";           // OK — var re-assignable
  // umur = 18;            // ERROR — final

  final sekarang = DateTime.now();  // OK — runtime
  // const sekarang2 = DateTime.now(); // ERROR — bukan compile-time

  print("$nama $umur $pi");
  print(sekarang);
}

void main() {
  print("42");
}

void main() {
  int umur = 17;
  double tinggi = 168.5;
  String nama = "Ari";
  bool aktif = true;
  num berapa = 42;    // menerima int ATAU double

  print("$nama $umur $tinggi $aktif");
  print(berapa);
  print(int.parse("42") + 8);
  print(3.9.toInt());  // 3 (dipotong)
  print("42".runtimeType);  // String
}

void main() {
  print(7 / 2);
  print(7 % 2);
}

Object bacaNilai() => "Ari";

void main() {
  print(7 / 2);    // 3.5
  print(7 ~/ 2);   // 3 — integer division
  print(7 % 2);    // 1

  Object nama = bacaNilai();
  print(nama is String);  // true
  print(nama is! int);    // true

  int? mungkin = null;
  print(mungkin ?? 0);    // 0
  mungkin ??= 10;         // assign jika null
  print(mungkin);         // 10
}

void main() {
  print("halo dunia");
}

void main() {
  String nama = "Ari";
  int umur = 17;

  print("$nama berumur ${umur + 1} tahun depan");

  String multi = """
Baris pertama
Baris kedua""";
  print(multi);

  print("halo".toUpperCase());
  print("  spasi  ".trim());
  print("5".padLeft(3, "0"));  // 005
  print(r"C:\folder");  // raw — backslash tetap
}

typedef Kali = int Function(int);

void main() {
  // buat fungsi kuadrat di sini
  print("buat di sini");
}

typedef IntList = List<int>;
typedef Operasi = int Function(int, int);

int tambah(int a, int b) => a + b;
int kali(int a, int b) => a * b;

void main() {
  IntList angka = [1, 2, 3];
  print(angka);
  Operasi hitung = tambah;
  print(hitung(3, 5));  // 8

  hitung = kali;
  print(hitung(3, 5));  // 15
}

void main() {
  var r = (10, 20);
  print(r.$1);
}

void main() {
  // positional
  var titik = (3, 7);
  print(titik.$1 + titik.$2);  // 10

  // named
  var user = (nama: "Ari", umur: 17);
  print("${user.nama} (${user.umur})");

  // destructuring
  var (x, y) = (10, 20);
  print("x=$x y=$y");

  // multi-return
  var (min, maks) = rentang([3, 8, 1, 9, 4]);
  print("$min..$maks");
}

(int, int) rentang(List<int> d) {
  return (d.reduce((a, b) => a < b ? a : b),
          d.reduce((a, b) => a > b ? a : b));
}

void main() {
  int nilai = 82;
  print("?");
}

void main() {
  int nilai = 82;
  String predikat = switch (nilai) {
    >= 90 => "A",
    >= 80 => "B",
    >= 70 => "C",
    _ => "D",
  };
  print(predikat);
}

String jelaskan(Object obj) => switch (obj) {
  _ => "tidak dikenal",
};

void main() => print(jelaskan([10, 20]));

String jelaskan(Object obj) => switch (obj) {
  0 => "nol",
  int n when n > 100 => "angka besar: $n",
  int n => "angka: $n",
  String s => "teks: $s",
  [int a, int b] => "pasangan: $a+$b=${a + b}",
  {"nama": String n} => "objek bernama $n",
  _ => "tidak dikenal",
};

void main() {
  print(jelaskan(0));
  print(jelaskan(42));
  print(jelaskan("halo"));
  print(jelaskan([3, 5]));
  print(jelaskan({"nama": "Ari"}));
}

void main() {
  int total = 0;
  print(total);
}

void main() {
  for (var i = 1; i <= 5; i++) print(i);

  var buah = ["apel", "mangga", "jeruk"];
  for (var b in buah) print(b);

  var stok = {"kopi": 12, "teh": 8};
  stok.forEach((k, v) => print("$k: $v"));
}

void main() {
  try {
    // throw di sini
  } catch (e) {
    print(e);
  }
}

int bagi(int a, int b) {
  if (b == 0) throw Exception("pembagi nol");
  return a ~/ b;
}

void main() {
  try {
    print(bagi(10, 2));
    print(bagi(10, 0));
  } on Exception catch (e) {
    print("Gagal: $e");
  } finally {
    print("Selesai.");
  }
}

void main() {
  print("tulis assert di sini");
}

class Hewan {
  void suara() => print("...");
}

class Kucing extends Hewan {
  @override
  void suara() => print("meong");
}

void main() {
  assert(1 + 1 == 2, "matematika rusak");
  Kucing().suara();
}

void main() {
  print("buat fungsi di sini");
}

int tambah(int a, int b) => a + b;
void sapa({String nama = "Tamu", int umur = 0}) => print("$nama ($umur)");

void main() {
  print(tambah(3, 5));
  sapa(nama: "Ari", umur: 17);
  sapa(nama: "Budi");
  sapa();
}

Function buat() {
  int n = 10;
  return () => n;
}

void main() {
  var next = buat();
  print(next());
}

Function buatPenghitung() {
  int hitung = 0;
  return () => ++hitung;
}

void main() {
  var next = buatPenghitung();
  print(next());  // 1
  print(next());  // 2
  print(next());  // 3

  var kuadrat = (int n) => n * n;
  print(kuadrat(7));  // 49
}

void main() {
  var d = [5, 3, 8, 1, 9];
  print(d);
}

void main() {
  var a = [1, 2, 3];
  var b = [0, ...a, 4];  // spread
  print(b);  // [0, 1, 2, 3, 4]

  var genap = [for (var i = 0; i <= 10; i++) if (i % 2 == 0) i];
  print(genap);  // [0, 2, 4, 6, 8, 10]

  var ada = a.contains(2);
  print(ada);
}

void main() {
  print({1, 2, 2, 3, 3, 3}.length);
}

void main() {
  var a = {1, 2, 3, 4, 5};
  var b = {4, 5, 6, 7, 8};
  print(a.union(b));
  print(a.intersection(b));
  print(a.difference(b));
  print([1, 2, 2, 3].toSet().length);  // 3
}

void main() {
  var m = {"a": 10, "b": 20};
  print(m);
}

void main() {
  var stok = {"kopi": 12, "teh": 8};
  stok["susu"] = 5;
  stok["teh"] = stok["teh"]! + 2;

  stok.forEach((k, v) => print("$k: $v"));
  print(stok.containsKey("matcha"));
  print(stok.length);
}

// buat fungsi generik terbesar<T extends num> di sini

void main() {
  print(terbesar([3, 8, 1, 9, 4]));
}

// hint: T terbesar<T extends num>(List<T> data) { ... }

T pertama<T>(List<T> list) => list.first;
double rata<T extends num>(List<T> d) => d.reduce((a, b) => a + b as T) / d.length;

void main() {
  print(pertama([1, 2, 3]));      // 1 (int)
  print(pertama(["a", "b"]));      // a (String)
}

class Siswa {
  String nama;
  int poin;
  Siswa(this.nama, this.poin);

  String info() => "?";
}

void main() => print(Siswa("Ari", 17).info());

class Siswa {
  String nama;
  int poin;

  Siswa(this.nama, this.poin);
  Siswa.kosong() : nama = "?", poin = 0;
  Siswa.istimewa(String n) : this(n, 100);
}

void main() {
  var a = Siswa("Ari", 17);
  var b = Siswa.kosong();
  var c = Siswa.istimewa("Budi");
  print("${a.nama} ${b.nama} ${c.nama}");
}

class Siswa {
  int poin = 75;
  // buat getter status di sini
}

void main() {
  print("buat getter di sini");
}

class Suhu {
  double _celsius = 0;

  double get celsius => _celsius;
  set celsius(double v) => _celsius = v;
  double get fahrenheit => _celsius * 9 / 5 + 32;
  set fahrenheit(double f) => _celsius = (f - 32) * 5 / 9;
}

void main() {
  var s = Suhu();
  s.celsius = 25;
  print(s.fahrenheit);  // 77
}

void main() {
  String? nama = null;
  print(nama);
}

int panjangWajib(String? teks) => teks!.length;

void tampilkan(String? nama) {
  print(nama ?? "Tamu");
  print(nama?.length);
}

void main() {
  tampilkan(null);       // Tamu, null
  tampilkan("Ari");      // Ari, 3
  print(panjangWajib("Ari")); // 3; ! menegaskan non-null

  late String deskripsi;
  deskripsi = "baru diisi";
  print(deskripsi);
}

abstract class Bentuk {
  double luas();
}

class Persegi extends Bentuk {
  double sisi;
  Persegi(this.sisi);

  @override
  double luas() => 0; // lengkapi
}

void main() => print(Persegi(4).luas());

abstract class Bentuk {
  double luas();
}

class Persegi extends Bentuk {
  double sisi;
  Persegi(this.sisi);
  @override
  double luas() => sisi * sisi;
}

void main() => print(Persegi(4).luas());

// buat mixin Halo di sini

class Item /* with Halo */ {
}

void main() {
  print("tulis mixin di sini");
}

mixin Loggable {
  void log(String msg) => print("[LOG] $msg");
}

mixin Greetable {
  String get nama;
  void sapa() => print("Halo $nama!");
}

class Item with Loggable, Greetable {
  @override
  String nama = "Widget";
}

void main() {
  var item = Item();
  item.log("dibuat");
  item.sapa();
}

enum Level { bronze, silver, gold }

void main() => print("?");

enum Level {
  bronze(1, "Bronze"),
  silver(2, "Silver"),
  gold(3, "Gold");

  final int nilai;
  final String label;
  const Level(this.nilai, this.label);

  @override
  String toString() => label;
}

void main() {
  print(Level.gold);       // Gold
  print(Level.gold.nilai);  // 3
  print(Level.values);
}

// buat extension Kuadrat on int di sini

void main() {
  print("buat extension di sini");
}

extension Kapital on String {
  String get kapitalAwal =>
      isNotEmpty ? "${this[0].toUpperCase()}${substring(1)}" : this;
  int get jumlahKata => trim().split(RegExp(r"s+")).length;
}

void main() {
  print("halo dunia".kapitalAwal);  // Halo dunia
  print("satu dua tiga".jumlahKata);  // 3
}

// buat extension type Email di sini

void main() {
  print("buat extension type di sini");
}

extension type Email(String _nilai) {
  bool get valid => _nilai.contains("@");
  String get teks => _nilai;
}

void main() {
  var email = Email("ari@kampus.com");
  print(email.valid);   // true
  print(email.teks);    // ari@kampus.com
}

sealed class Bentuk {}
class Persegi extends Bentuk { final double sisi; Persegi(this.sisi); }
class Lingkaran extends Bentuk { final double r; Lingkaran(this.r); }

double luas(Bentuk b) => switch (b) {
  // lengkapi pola di sini
  _ => 0,
};

void main() => print(luas(Persegi(4)));

sealed class Bentuk {}
class Persegi extends Bentuk { final double sisi; Persegi(this.sisi); }
class Lingkaran extends Bentuk { final double r; Lingkaran(this.r); }

double luas(Bentuk b) => switch (b) {
  Persegi(sisi: var s) => s * s,
  Lingkaran(r: var r) => 3.14159 * r * r,
};

void main() {
  print(luas(Persegi(4)));
  print(luas(Lingkaran(7)));
}

class Diskon {
  double persen;
  Diskon(this.persen);

  // buat method call di sini
}

void main() {
  var d = Diskon(50);
  print("lengkapi call()");
}

class Diskon {
  double persen;
  Diskon(this.persen);

  double call(double harga) => harga * (1 - persen / 100);
}

void main() {
  var diskon20 = Diskon(20);
  print(diskon20(100000));  // 80000
}

Future<void> main() async {
  // await Future.value(42) di sini
  print("lengkapi");
}

Future<String> ambilData() async {
  await Future.delayed(Duration(milliseconds: 100));
  return "data tiba";
}

Future<void> main() async {
  print("mulai");
  var hasil = await ambilData();
  print(hasil);

  var paralel = await Future.wait([
    Future.value(10),
    Future.value(20),
  ]);
  print(paralel.reduce((a, b) => a + b));  // 30
}

Stream<int> hitung(int n) async* {
  for (var i = 1; i <= n; i++) yield i;
}

Future<void> main() async {
  int total = 0;
  // await for di sini
  print(total);
}

Stream<int> hitung(int n) async* {
  for (var i = 1; i <= n; i++) {
    await Future.delayed(Duration(milliseconds: 10));
    yield i;
  }
}

Future<void> main() async {
  await for (var x in hitung(5)) {
    print(x);
  }
}

void main() {
  // hitung total 1..100 di sini
  print(0);
}

import "dart:isolate";

Future<void> main() async {
  var hasil = await Isolate.run(() {
    var total = 0;
    for (var i = 1; i <= 1000000; i++) total += i;
    return total;
  });
  print(hasil);  // 500000500000
}

import "dart:math" as m;

void main() {
  print("gunakan m.max di sini");
}

import "dart:math" as m;

void main() {
  print(m.max(3, 8));
  print(m.min(3, 8));
  print(m.pow(2, 10));
}

import "dart:convert";

void main() {
  print("encode/decode di sini");
}

import "dart:convert";

void main() {
  var data = {"nama": "Ari", "umur": 17};
  var teks = jsonEncode(data);
  print(teks);

  var balik = jsonDecode(teks) as Map<String, dynamic>;
  print(balik["nama"]);
}

int bagi(int a, int b) {
  if (b == 0) throw Exception("nol");
  return a ~/ b;
}

void main() {
  print("susun kasus di sini");
}

// Untuk proyek lokal, jalankan suite test dengan dart test.
// DartPad menjalankan pemeriksaan assert sederhana berikut.
int tambah(int a, int b) => a + b;

void main() {
  assert(tambah(2, 3) == 5, "tambah(2,3) harus 5");
  assert(tambah(0, 0) == 0, "tambah(0,0) harus 0");
  assert(tambah(-1, 1) == 0, "tambah(-1,1) harus 0");
  print("3/3 lulus");
}