Groovy如何處理閉包作用域和遞歸？

Question

我有一個遞歸的Python函數，它可以構建樹，並且正在嘗試將其轉換為Groovy。

這是Python版本...

def get_tree(vertices):
    results = []

    if type(vertices) != list:
        vertices = [vertices]

    for vertex in vertices:
        results.append(vertex)
        children = get_children(vertex)
        if children:
            child_tree = get_tree(children)
            results.append(child_tree)

    return results

這是get_tree（1）的輸出...

  [1, [2, 3, 4, [5, 3]]]

這是我嘗試將其轉換為Groovy閉包...

_tree = { vertices ->

  results = []

  vertices.each() {
    results << it
    children = it."$direction"().toList()
    if (children) {
      child_tree = _tree(children)
      results << child_tree
    }
  }
  results
}

但這不起作用-這就是它的返回值...

gremlin> g.v(1).outTree()    
==>[v[5], v[3], (this Collection), (this Collection)]

這些“收藏”是關於什么的？

我對Groovy只是一個粗略的了解，我懷疑這與Groovy如何處理遞歸和關閉范圍有關。

請賜教我:)

Answer 1

解決方案是將def添加到results = [] ：

_tree = { vertices ->

  def results = []

  vertices.each() {
    results << it
    children = it."$direction"().toList()
    if (children) {
      child_tree = _tree(children)
      results << child_tree
    }
  }
  results
}

請參閱https://groups.google.com/d/msg/gremlin-users/iCPUifiU_wk/mrUhsjOM2h0J