import 'dart:core';

void main() {
  // Unlike arrays, lists in Dart are dynamically sized.
  // An uninitialized list is equal to null and has length 0.
  List<String>? s;
  print("uninit: $s ${s == null} ${s?.length == 0}");

  // To create an empty list with non-zero length, we can use
  // the List constructor. Here we create a list of strings
  // with length 3 (initially filled with null values).
  s = List<String>.filled(3, '');
  print("emp: $s len: ${s.length} cap: ${s.length}");

  // We can set and get elements just like with arrays.
  s[0] = "a";
  s[1] = "b";
  s[2] = "c";
  print("set: $s");
  print("get: ${s[2]}");

  // length returns the length of the list as expected.
  print("len: ${s.length}");

  // Lists in Dart can be easily expanded using the add method.
  s.add("d");
  s.addAll(["e", "f"]);
  print("apd: $s");

  // We can create a copy of a list using the spread operator.
  var c = [...s];
  print("cpy: $c");

  // Lists support slicing with the sublist method.
  var l = s.sublist(2, 5);
  print("sl1: $l");

  // This slices up to (but excluding) index 5.
  l = s.sublist(0, 5);
  print("sl2: $l");

  // And this slices from (and including) index 2 to the end.
  l = s.sublist(2);
  print("sl3: $l");

  // We can declare and initialize a list in a single line as well.
  var t = ["g", "h", "i"];
  print("dcl: $t");

  // Dart provides various utility methods for lists.
  var t2 = ["g", "h", "i"];
  if (listEquals(t, t2)) {
    print("t == t2");
  }

  // Lists can be composed into multi-dimensional data structures.
  // The length of the inner lists can vary.
  var twoD = List.generate(3, (i) => List.generate(i + 1, (j) => i + j));
  print("2d: $twoD");
}

// A simple implementation of listEquals for demonstration
bool listEquals<T>(List<T> a, List<T> b) {
  if (a.length != b.length) return false;
  for (var i = 0; i < a.length; i++) {
    if (a[i] != b[i]) return false;
  }
  return true;
}