From: Jason Creighton <androflux@...>
Date: 2003-07-22T01:02:53+09:00
Subject: Re: Proposal: Array#to_h, to simplify hash generation

On Mon, 21 Jul 2003 05:32:25 GMT
Martin DeMello <martindemello@yahoo.com> wrote:

> To me, 'hashify' implies taking an assoc array and converting it to hash
> form (or perhaps the perl-influenced [a, b, c, d] -> {a=>b, c=>d}). I
> still can't think of a name for the useful case :) make_hash, perhaps ..
> 
> *(1..10).make_hash {|i| f(i)}
> 
> or maybe the complementary hash_to and hash_from, where the block is
> respectively the value and the key for the corresponding array entry :)

I'd like the code to be something like this:

module Enumerable
  def to_h
    h = Hash.new
    if block_given?
      self.each { |e| h[e] = yield(e) }
    else
      self.each { |key, value| h[key] = value }
    end
    return h
  end
end

>> (1..5).to_h { |n| n*n }
=> {5=>25, 1=>1, 2=>4, 3=>9, 4=>16}
>> [ [1,2], [3,4] ].to_h
=> {1=>2, 3=>4}
>> [ [1,2], [3,4] ].to_h.to_a
=> [[1, 2], [3, 4]]
>> [ [1,2], [3,4] ].to_h.to_a.to_h
=> {1=>2, 3=>4}
>> Dir["/bin/d*"].to_h { |f| File.size(f) }
=> {"/bin/dnsdomainname"=>9332, "/bin/date"=>25728, "/bin/dd"=>29492, "/bin/dmesg"=>3924, "/bin/df"=>27368, "/bin/domainname"=>9332}

I would almost prefer [1,2,3,4].to_h => {1=>2, 3=>4}, but Hash#to_h returns a
nested array, so that's what this code does. Plus it's easier to implement. :-)

Jason Creighton