在新结构中快速创建结构列表 [英] Quickly creating a list of structs in a new struct

问题描述

我正在尝试构建一些原始对象来存储图形:

I'm trying to build a few primitive objects to store a graph:

Vertex = Struct.new(:parent, :rank)
Graph = Struct.new(:vertexes, :edges)
Edge = Struct.new(:weight, :endpoints)

这里的想法是:endpoints (和:parent )是顶点，并且，自然地， Graph 存储顶点和边的列表.我试图进行设置，但遇到了麻烦:

The idea here is that :endpoints (and :parent) are Vertexes, and, naturally, Graph stores lists of Vertexes and Edges. I tried to set this up, and I ran into trouble:

[47] pry(main)> t_graph = Graph.new()
=> #<struct Graph vertexes=nil, edges=nil>
[48] pry(main)> t_graph[:vertexes] = Array.new(Vertex.new())
TypeError: can't convert Vertex into Integer
from (pry):48:in `initialize'

另一方面，这可行:

[49] pry(main)> t_graph[:vertexes] = [Vertex.new(), Vertex.new()]
=> [#<struct Vertex parent=nil, rank=nil>,
 #<struct Vertex parent=nil, rank=nil>]

在图形(或任何此类关系)中生成大量空顶点进行测试的有效方法是什么?

What's the efficient way to generate a mass of empty Vertexes in a Graph (or any such relation) for testing?

推荐答案

一种简单填充顶点列表的方法是使用 .times ，这看起来有点笨拙，但是会创建一个列表(我添加了:id 值):

One way to simply populate a list of Vertexes is to use .times, which seems kind of clumsy, but creates a list (I added an :id value):

t_verts = []
9.times do t_verts << Vertex.new end
[10] pry(main)> t_verts
=> [#<struct Vertex parent=nil, rank=nil, id=nil>,
 #<struct Vertex parent=nil, rank=nil, id=nil>,
 #<struct Vertex parent=nil, rank=nil, id=nil>,
 #<struct Vertex parent=nil, rank=nil, id=nil>,
 #<struct Vertex parent=nil, rank=nil, id=nil>,
 #<struct Vertex parent=nil, rank=nil, id=nil>,
 #<struct Vertex parent=nil, rank=nil, id=nil>,
 #<struct Vertex parent=nil, rank=nil, id=nil>,
 #<struct Vertex parent=nil, rank=nil, id=nil>]

这将创建不同的对象.

[11] pry(main)> t_verts.each do |vert|
[11] pry(main)*   vert.id = rand  
[11] pry(main)* end  
=> [#<struct Vertex parent=nil, rank=nil, id=0.755245226082449>,
 #<struct Vertex parent=nil, rank=nil, id=0.0167377598961559>,
 #<struct Vertex parent=nil, rank=nil, id=0.759799975185007>,
 #<struct Vertex parent=nil, rank=nil, id=0.613897002692335>,
 #<struct Vertex parent=nil, rank=nil, id=0.0407847317079812>,
 #<struct Vertex parent=nil, rank=nil, id=0.549475744759297>,
 #<struct Vertex parent=nil, rank=nil, id=0.571876769381891>,
 #<struct Vertex parent=nil, rank=nil, id=0.270800829904956>,
 #<struct Vertex parent=nil, rank=nil, id=0.814754555208641>]

要将这些整体添加到图中，可以使用Simone的方法将顶点列表添加到图中:

To add these en masse to a Graph, Simone's method can be used to add the list of Vertexes to the Graph:

def add_vertex(new_verts) # Adds or updates vertexes non-destructively
    new_verts.each do |new_vert|
      # first case, redundant insert
      if self.vertexes.include?(new_vert)
        warn "Vertex already exists in graph, no replacement done"
        # second case, update
      elsif not (update_vert = self.vertexes.select { |vert| vert.id == new_vert.id }).empty?
        self.vertexes[self.vertexes.index(update_vert)] = new_vert
        # third case, append new
      else
        self.vertexes ||= []
        self.vertexes << vertex
      end
    end
  end

似乎我需要构建一个构造器方法，该方法从邻接列表和权重列表构建Graph；我看不出有一个简单的方法可以一步一步完成.

It looks like I need to build a constructor method that builds the Graph from an adjacency list and weight list; I don't see a simple way to do this in one big step.

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