From: google@... (Tom Payne)
Date: 2003-01-17T20:05:34+09:00
Subject: Feature request: Array.to_h

I use the following snippet a lot, and think it's worth including in
the Ruby built-in Array class.

class Array

  def to_h(default = nil)
    result = Hash.new(default)
    each_with_index do |value, index|
      result[index] = value
    end
    result
  end

end

Example usage:

[:a, :b, :c].to_h # => {0=>:a, 1=>:b, 2=>:c}

I often use it in processing comma-separated variable (CSV) files with
a header row, for example:

header_row = "year,month,day,price\n"
index_of = header_row.chomp.split(',').to_h.invert
# => {"month"=>1, "price"=>3, "day"=>2, "year"=>0}
data_row = "2002,1,17,1.5\n"
cells = data_row.chomp.split(',')