Clear Case of Unclear Casing

Recent Ruby versions allow you to choose from a wide-range of uppercase letters - beyond just ASCII - to start a constant / class name:

class Österreich
  # 00D6 ├─ Ö   ├─ LATIN CAPITAL LETTER O WITH DIAERESIS
end
# Syntax OK

However, it is not possible to use just any Unicode character:

class ℻
  # 213B ├─ ℻   ├─ FACSIMILE SIGN
end
# SyntaxError

Only characters of the categories Uppercase_Letter or Titlecase_Letter of your current Ruby's Unicode version are allowed. This can be trickier that you might think at first, as illustrated here:

class 🅆
  # 1F146 ├─ 🅆    ├─ SQUARED LATIN CAPITAL LETTER W
end
# Syntax OK

class 🅏
  # 1F14F ├─ 🅏    ├─ SQUARED WC
end
# SyntaxError

Or consider this case:

class 𐲄
  # 10C84 ├─ 𐲄    ├─ OLD HUNGARIAN CAPITAL LETTER EC
end
# Syntax OK

class 🡓
  # 1F853 ├─ 🡓    ├─ DOWNWARDS SANS-SERIF ARROW
end
# SyntaxError

Start a Class

For reference, this is the list of allowed characters to start a class/constant, as of Ruby 3.0:

Also See

• The Ruby patch which introduced this feature
• uniscribe: Utility for Unicode codepoint analysis (used in the examples)

More Idiosyncratic Ruby

• Please Comment on GitHub
• Next Article: Unicode Version Mapping
• Previous Article: Nothing to Disable