Feature #5550

Hash#depth, Hash#flat_length for recursive hashes

Added by Tsuyoshi Sawada almost 4 years ago. Updated almost 3 years ago.



I often have a hash whose value is recursively a hash, which may look like the following:

{"Japan" =>
    {"Hokkaido" => "Sapporo", ...},
    {"Honhuu" =>
        {"Aomori" => "Hirosaki", ...},
        {"Akita" => ...},
    {"Shikoku" => ...},

In these cases, it will be convenient if there is a way to know the (maximum) depth of he original hash, and the numbers of all the "terminal nodes". I would like to propose two methods Hash#depth and Hash#flat_length, whose Ruby implementation can be as follows:

class Hash
def depth
    1 + (values.map{|v| Hash === v ? v.depth : 1}.max)
def flat_length
    values.inject(0){|sum, v| sum + (Hash === v ? v.flat_length : 1)}


#1 Updated by Yukihiro Matsumoto almost 4 years ago

  • Status changed from Open to Feedback

わずか6行のmonkey patchingを避けるためにすべてのRubyに追加すべきメソッドですか?

#2 Updated by Alexey Muranov almost 4 years ago

Excuse me, can you be more precise with your example please? Ruby does not accept it (after removing the dots "..."). Are you talking about nested hashes? How about creating a class Tree that would inherit from Hash and define additional methods there?

#3 Updated by Thomas Sawyer almost 4 years ago

I take it you meant nested hash. I think your methods will infinite loop on recursive hash --and that needs to be considered.

I understand #depth, Array might use such a method too. But #flat_length, I don't quite get what is being counted.

#4 Updated by Yusuke Endoh almost 3 years ago

  • Status changed from Feedback to Rejected

No feedback, looks hopeless to me. Closing.

Yusuke Endoh mame@tsg.ne.jp

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