Haxe不支持像 C 中传统的 for 循环。它的 for关键字期望一个开口的圆括号 (，然后一个变量标识符，之后一个关键字 in，和一个任意表达式作为迭代的集合；在闭口的圆括号 ) 之后，是任意的循环体表达式。
Haxe does not support traditional for-loops known from C.Its for keyword expects an opening parenthesis (, then a variable identifier followed by the keyword in and an arbitrary expression used as iterating collection. After the closing parenthesis ) follows an arbitrary loop body expression.
for (v in e1) e2; 类型工具确保 e1 的类型可以被迭代，典型的情况是是否有一个iterator方法返回一个Iterator类型，或者它本身是一个 Iterator类型。
The typer ensures that the type of e1 can be iterated over, which is typically the case if it has an iterator method returning an Iterator, or if it is an Iterator itself.
变量 v 然后可以在循环体 e2 中使用，保存了e1集合的某个个体元素。
Variable v is then available within loop body e2 and holds the value of the individual elements of collection e1.
Haxe有一个特别的范围操作符控制迭代次数。这是一个二院操作符，操作两个操作数：min...max，返回一个从min（包括）到max（不包括）的IntIterator类型的实例。注意，max不能小于min。
Haxe has a special range operator to iterate over intervals. It is a binary operator taking two Int operands: min...max returns an IntIterator instance that iterates from min (inclusive) to max (exclusive). Note that max may not be smaller than min.
for (i in 0...10) trace(i); // 0 to 9 for表达式的类型总是 Void ，也就是说没有值可以被使用作为右侧表达式。
The type of a for expression is always Void, meaning it has no value and cannot be used as right-side expression.
循环的控制流被 break（第5.20节）表达式影响，也受 continue（第5.21节）表达式影响。
The control flow of loops can be affected by break (5.20) and continue (5.21) expressions.