return false
		case 'A' <= r && r <= 'Z':
			return false
		case r == '_':
			return false
		}
		return true
	}
	// Letters and digits are not separators
	if unicode.IsLetter(r) || unicode.IsDigit(r) {
		return false
	}
	// Otherwise, all we can do for now is treat spaces as separators.
	return unicode.IsSpace(r)
}

pkg unicode, const UpperLower ideal-char
pkg unicode, const Version ideal-string
pkg unicode, func Is(*RangeTable, int32) bool
pkg unicode, func IsControl(int32) bool
pkg unicode, func IsDigit(int32) bool
pkg unicode, func IsGraphic(int32) bool
pkg unicode, func IsLetter(int32) bool
pkg unicode, func IsLower(int32) bool
pkg unicode, func IsMark(int32) bool
pkg unicode, func IsNumber(int32) bool