GSM 03.38 basic character set (“GSM-7”) in Ruby

gsm7.rb

require 'set'

module GSM7
  # https://en.wikipedia.org/wiki/GSM_03.38#GSM_7-bit_default_alphabet_and_extension_table_of_3GPP_TS_23.038_/_GSM_03.38
  BASIC_CHARACTER_SET = Set.new([
    "\n", "\r", " ", "!", "\"", "#", "$", "%", "&", "'", "(", ")", "*", "+", ",", "-", ".", "/", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", ":", ";", "<", "=", ">", "?", "@", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "_", "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "¡", "£", "¤", "¥", "§", "¿", "Ä", "Å", "Æ", "Ç", "É", "Ñ", "Ö", "Ø", "Ü", "ß", "à", "ä", "å", "æ", "è", "é", "ì", "ñ", "ò", "ö", "ø", "ù", "ü", "Γ", "Δ", "Θ", "Λ", "Ξ", "Π", "Σ", "Φ", "Ψ", "Ω"
  ]).freeze

  def self.basic_characters_only?(string)
    Set.new(string.chars).subset?(BASIC_CHARACTER_SET)
  end
  
  def self.non_basic_characters(string)
    Set.new(string.chars).difference(BASIC_CHARACTER_SET)
  end
end


# Emojis are not allowed
GSM7.basic_characters_only? 'Halloween party tonight 🎃👻'      #=> false
GSM7.non_basic_characters   'Halloween party tonight 🎃👻'      #=> #<Set: {"🎃", "👻"}>
GSM7.basic_characters_only? 'Halloween party tonight!'          #=> true
GSM7.non_basic_characters   'Halloween party tonight!'          #=> #<Set: {}>

# Smart quotes and dashes are not allowed
GSM7.basic_characters_only? 'Lorem “ipsum” dolor – sit amet'    #=> false
GSM7.non_basic_characters   'Lorem “ipsum” dolor – sit amet'    #=> #<Set: {"“", "”", "–"}>
GSM7.basic_characters_only? 'Lorem "ipsum" dolor -- sit amet'   #=> true
GSM7.non_basic_characters   'Lorem "ipsum" dolor -- sit amet'   #=> #<Set: {}>

# Square brackets are not allowed
GSM7.basic_characters_only? '7:30 show: VIEW FROM MY [SIC] BED' #=> false
GSM7.non_basic_characters   '7:30 show: VIEW FROM MY [SIC] BED' #=> #<Set: {"[", "]"}>
GSM7.basic_characters_only? '7:30 show: VIEW FROM MY (SIC) BED' #=> true
GSM7.non_basic_characters   '7:30 show: VIEW FROM MY (SIC) BED' #=> #<Set: {}>

# Only basic Western European characters are supported
GSM7.basic_characters_only? 'école mañana façade könig værdi'   #=> true
GSM7.basic_characters_only? '道可道非常道，名可名非常名。'          #=> false