Issue #7793 has been updated by Andrew M.


FYI, Rails has a method similar to the proposed `map_k` called [`transform_keys`](http://api.rubyonrails.org/classes/Hash.html#method-i-transform_keys-21).

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Feature #7793: New methods on Hash
https://bugs.ruby-lang.org/issues/7793#change-47248

* Author: Dominic Sisneros
* Status: Assigned
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* Category: core
* Target version: next minor
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=begin
It would be nice to have the following methods added to hash

  h = { name: 'dominic', request: 'add the following methods', :why => 'convenience'}

  h.map_v{|v| v.upcase}
  #=> {:name=>"DOMINIC", :request=>"ADD THE FOLLOWING METHODS", :why=>"CONVENIENCE"}

  h.map_k{|k| k.to_s}
  #=> { "name"=> 'dominic', "request"=>"add the following methods', "why" => "convenience"}

  h.map_kv{|k,v| [k.to_s, v.upcase]}
  #=> { "name"=>"DOMINIC", "request"=>"ADD THE FOLLOWING METHODS", "why"=>"CONVENIENCE"}


  class Hash

    def map_v
      reduce({}) do |result, array|
        k,v = array
        new_val = yield v
        result.merge( k => new_val)
      end
    end

    def map_k
      reduce({}) do |result, array|
        k,v = array
        new_k = yield k
        result.merge(new_k => v)
      end
    end

    def map_kv
      reduce({}) do |result, array|
        new_k,new_v = yield array
        result.merge(new_k => new_v)
      end
    end

  end
=end




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