Downcase, upcase and “delatin” functions for strings in cyrillic

cyr_functions.rb

# encoding: utf-8

class String
  def cyr_downcase
    self
      .unpack("U*")
      .map { |c| if (1040..1071) === c then (c + 32) elsif (1025 == c) then 1105 else c end }
      .pack("U*")
  end
  
  def cyr_upcase
    self
      .unpack("U*")
      .map { |c| if (1072..1103) === c then (c - 32) elsif (1105 == c) then 1025 else c end }
      .pack("U*")
  end
  
  def cyr_delatin
    # Some latin symbols look like cyrillic ones.
    # String#cyr_delatin substitutes the former with the latter.
    h = {
      'A' => 'А', 'B' => 'В', 'E' => 'Е', 'K' => 'К', 'M' => 'М', 'H' => 'Н', 'O' => 'О',
      'P' => 'Р', 'C' => 'С', 'T' => 'Т', 'X' => 'Х',
      'a' => 'а', 'e' => 'е', 'y' => 'у', 'x' => 'х'
      }
    self.chars.map { |c| if h.has_key?(c) then h[c] else c end }.join
  end
end