Entry tags:
on the verge of introducing Y-combinator
isAncestor = function(ancestor) {
var check = function(descendant) {
var p = descendant && descendant.parentNode
return ancestor === p || !!(p && check(p))
};
return check
}
visitor pattern, scala sample
scala> abstract class N[T]
defined class N
scala> case class L[T](v:T) extends N[T]
defined class L
scala> case class B[T](kids:List[N[T]]) extends N[T]
defined class B
scala> val t = B(List(B(List(L("ab"),L("cd"),B(List(L("xy"),L("z"))))),L("middle")))
t: B[java.lang.String] = B(List(B(List(L(ab), L(cd), B(List(L(xy), L(z))))), L(middle)))
scala> def scan[T](tree:N[T]):List[T] = tree match { case L(v) => List(v); case B(kids) => kids flatMap (scan(_)) }
scan: [T](N[T])List[T]
scala> scan(t)
res17: List[java.lang.String] = List(ab, cd, xy, z, middle)
scala>
I used repl, so it's kind of too laconic; in real life you probaly won't call your class N, L and B. But you know what I mean, right?