Groovy 如何处理闭包范围和递归？

发布于 2024-11-30 16:19:48 字数 1044 浏览 1 评论 0原文

我有一个递归 Python 函数来构建一棵树，我正在尝试将其转换为 Groovy。

这是 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

这是 get_tree(1) 的输出...

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

这是我尝试将其转换为 Groovy 闭包...

_tree = { vertices ->

  results = []

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

但这不起作用 - 这就是它返回的...

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

什么是那些“这个集合”是关于什么的？

我对 Groovy 只有粗略的了解，我怀疑这与 Groovy 处理递归和闭包作用域的方式有关。

请赐教:)

原文

I have a recursive Python function that builds a tree, and I'm trying to translate it into Groovy.

Here's the Python version...

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

Here's the output of get_tree(1)...

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

And here's my attempt to translate this into a Groovy closure...

_tree = { vertices ->

  results = []

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

But this doesn't work -- this is what it returns...

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

What are those "this Collection"s about?

I have only a cursory understanding of Groovy, and I suspect it's something to do with how Groovy handles recursion and closure scope.

Please enlighten me :)

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愁杀 2024-12-07 16:19:48

解决方案是将 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
}

请参阅 https://groups.google.com/d/msg/gremlin-users/iCPUifiU_wk/mrUhsjOM2h0J

The solution was to add def to results = []:

_tree = { vertices ->

  def results = []

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

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

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