Variables

import 'dart:math'; //use math library

//Comment

///Doc comment
/// # header
/// - list

// main - program start point
void main() {   //function body

  //variable declaration
  var z; //dynamic type
  z = 1; z = 1.0; z = 'one'; //don’t do that

  //all is Object - no primitive types!
  Object? v = null; //can be null

  //Subclassing from Object -> num -> int or double
  //Methods: round, truncate, toInt, toDouble, parse
  print('10.isEven: ${10.isEven}'); //print expression

  //type inference when assigning value
  var w = 1; //int - 1 is integer, 1.0 is double, ...

  //Type-safe - static typing
  w = 5; //type int can store only integers

  //statement with expression x = 5 / 2
  // ~/ - truncating division operator
  var x = 5 / 2; //decimal number 2.5 by default
  print('5 / 2 = $x'); //print variable

  //call a function from math library
  var y = sin(45 * pi / 180); //min, max, sqrt, sin, cos

  //Immutability: Const -> final -> var
  const PI = 3.14; //compile time constant
  final t = DateTime.now().hour; //runtime constant

  //arithmetic operators
  var c = 0;
  c = c + 1; // +, -, *, /, ~/, %
  c += 1; // +=, -=, *=, /=, ~/=, %=
  c++; //c++, c--, ++c, --c
  print(c);

}