From: "marcandre (Marc-Andre Lafortune)" <ruby-core@...>
Date: 2012-07-22T06:51:39+09:00
Subject: [ruby-core:46599] [ruby-trunk - Feature #6669] A method like Hash#map but returns hash


Issue #6669 has been updated by marcandre (Marc-Andre Lafortune).


Hi,

duerst (Martin D��rst) wrote:
>  Wouldn't it be really confusing that for Arrays, #map and #collect are 
>  synonyms, but for Hash, they are different?

It could be confusing, and would also introduce incompatibilities. Also, if the proposal for associate/categorize is accepted, then this `collect` would be a duplication.

I believe that methods like associate/categorize acting on all Enumerable to produce Hashes would be far more useful (since they don't only act on hashes), without introducing incompatibilities.
----------------------------------------
Feature #6669: A method like Hash#map but returns hash
https://bugs.ruby-lang.org/issues/6669#change-28264

Author: yhara (Yutaka HARA)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: 2.0.0


=begin
Given a hash h, h.map returns an array(alist), but sometimes I hope it returned a hash.

Example:

  class Hash
    def apply(&block)
      self.inject({}) do |h, (k, v)|
        new_k, new_v = *block.call(k, v)
        h[new_k] = new_v
        h
      end
    end
  end
  
  score = {
    taro: [1,3,2], 
    jiro: [3,5,8,4], 
    saburo: [2,9]
  }
  max_score = score.apply{|k,v| [k, v.max]}
  #=> {taro: 3, jiro: 8, saburo: 9}
  p max_score[:taro]
  #=> 3

I'm not thinking "apply" is a perfect name for this. Maybe "hash_map" is better
(we already have "flat_map").
=end



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