From: Robert Klemme <shortcutter@...>
Date: 2011-05-03T16:30:21+09:00
Subject: Re: Help making a method more concise

On Tue, May 3, 2011 at 6:28 AM, Christopher Dicely <cmdicely@gmail.com> wrote:
> On Mon, May 2, 2011 at 11:17 AM, Mark Hayes <mark@deployfx.com> wrote:
>> Hello,
>>
>> I'm looking to improve my skills as a Rubyist and would like to know if the
>> "depth" method could be expressed more precisely.  Any help would be greatly
>> appreciated, thanks!
>>
>> require 'test/unit'
>>
>> class Node
>>  attr_accessor :value, :lchild, :rchild
>>
>>  def depth
>>    [lchild ? lchild.depth : 0, rchild ? rchild.depth : 0].max + 1
>>  end
>> end
>
>
> def depth
>  1 + [lchild,rchild].map {|ch| [ch}.max
> end

Does not work: apart from the syntax invocation of #depth is missing.
If we add that we have a solution that has been proposed already.

> or even:
>
> def depth
>   1 + [lchild,rchild].map(&:to_i).max
> end
>
> alias to_i depth

Now that's an interesting idea to use the knowledge that nil.to_i => 0!

> or:
>
> add empty (no value) left & right children when you first add a value
> to a node, and:
>
> def empty?
>  @value.nil?
> end
>
> def depth
>  empty? ? 0 : [lchild,rchild].map(&:depth).max
> end

I don't think this captures the original semantics properly.  Now
there are only two states: empty, not empty.  But the original design
allowed for more states: empty, left set, right set, both set.  Even
if not for #depth this is likely important for other tree algorithms.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/