People used to do it this way:

hash = {}
input.each do |item|
  hash[item] = process(item)
end
hash

: (

Two solutions:

# from http://www.h6.dion.ne.jp/~machan/misc/FPwithRuby.html
module Enumerable
  def mash(&block)
    self.inject({}) do |output, item|
      key, value = block_given? ? yield(item) : item
      output.merge(key => value)
    end
  end
end

module Enumerable
  def mash(&block)
    Hash[self.map do |item|
      if block_given?
        yield(item)
      else
        nil
      end
    end]
  end
end

syntax

pry > ["I", "love", "Ruby"].mash { |w| [w, w.size] }
=> {"I"=>1, "love"=>4, "Ruby"=>4}

Which one do you prefer?