dart_basics/lib/basic_part1.dart

void basic_build_in_types() {
  // Numbers - (int, double) num
  // Booleans - true 或 false
  // Lists - Collections of items (aka arrays)
  // Sets - Collection of unique items (Dart 2.2 正式引入)
  // Maps - Collections with associated Key Value Pairs
  // Strings - "Hello!" (single and double quotes)
  // Runes - unicode character points
  // Symbols - #symbol (simbolic metadata)

  int x = 1;
  int hex = 0xFA;
  print("int: $x, hex int: $hex");

  double y = 1.1;
  double exponents = 1.42e5;
  print("double: $y, exponents: $exponents");

  // String <=> int
  int one = int.parse('1');
  assert(one == 1);
  String oneAsString = 1.toString();
  assert(oneAsString == '1');

  // String <=> double
  double onePointOne = double.parse('1.1');
  assert(onePointOne == 1.1);
  String piAsString = 3.14159.toStringAsFixed(2);
  assert(piAsString == '3.14');

  // Bitwise 運算
  assert((3 << 1) == 6); // 0011 << 1 == 0110
  assert((3 >> 1) == 1); // 0011 >> 1 == 0001
  assert((3 | 4) == 7); // 0011 | 0100 == 0111

  // Check for zero.
  int hitPoints = 0;
  assert(hitPoints <= 0);
  print("hitPoints <= 0? ${hitPoints <= 0}");


  print("\nDart Strings:");
  String str1 = "It's a string with double quotes";
  String str2 = 'It\'s a string with single quote';
  String str3 = """
  It's a long string with triple double quotes
  這是一個很長的字串
  """;
  print(str1);
  print(str2);
  print(str3);

  const aConstNum = 0;
  const aConstBool = true;
  const aConstString = 'a constant string';

  var aNum = 0;
  var aBool = true;
  var aString = 'a string';
  const aConstList = [1, 2, 3];

  const validConstString = '$aConstNum $aConstBool $aConstString';
  // const invalidConstString = '$aNum $aBool $aString $aConstList';
  print("validConstString: $validConstString");
  print("$aNum $aBool $aString $aConstList, ${aConstList[0]}");


  print("\nDart List:");
  // List & Generics(泛型)
  List<String> fruits = ['bananas', 'grapes', 'oranges'];
  print(fruits);
  print("fruits.length: ${fruits.length}");
  print("fruits[1]: ${fruits[1]}");

  fruits[1] = "apples";
  print(fruits);

  fruits.sort();
  print(fruits);

  fruits = fruits.map((String fruit) {
    return fruit.substring(0, fruit.length - 1);
  }).toList();
  print(fruits);


  print("\nDart Set:");
  // Set
  Set<String> halogens = {'fluorine', 'chlorine', 'bromine', 'iodine', 'astatine'}; // 鹵元素 氟氯溴碘砈
  print(halogens);

  var elements = <String>{};
  elements.add('fluorine');
  elements.addAll(halogens);


  print("\nDart Map:");
  // Map
  Map gifts = {
    // Key:    Value
    'first': 'partridge',
    'second': 'turtledoves',
    'fifth': 'golden rings'
  };
  print("gifts.length: ${gifts.length}");
  print("gifts['first']: ${gifts['first']}");

  // 惰性氣體
  Map<int, String> nobleGases = {
    2: 'helium',
    10: 'neon',
    18: 'argon',
  };
  print(nobleGases.containsValue("argon"));
}

void basic_function() {
  print("\nDart Function:");
  // Function
  dynamic_add(a, b) {
    return a + b;
  }
  print(dynamic_add(1, 2));
  print(dynamic_add(20.0, 40.0));
  print(dynamic_add("a", "b"));

  int add(int a, int b) {
    return a + b;
  }

  Function func = add;
  var result = func(20, 30);
  print("func result is $result");

  Map ops = {
    'add': add,
    'sub': (int a, int b) => a - b,
  };
  result = ops['sub'](6, 10);
  print("ops sub result: $result");
}