Decimal numbers may have an optional leading plus, minus, or not sign followed by a decimal digit and additional digits or underscores. They cannot have leading or trailing underscores.

DecimalInteger := ['+' | '-' | '~']  DecimalDigit  ('_'*  DecimalDigit)*

DecimalDigit   := '0' to '9'

Hexadecimal, octal, or binary numbers have an optional sign, a prefix indication the radix, and is followed by digits corresponding to the radix and underscores. They may not have trailing underscores.

RadixInteger  := ['+' | '-' | '~']  {HexInteger | OctalInteger | BinaryInteger}

HexInteger    := '#'  HexDigit  ('_'*  HexDigit)*

HexDigit      := Digit | 'A' to 'F' | 'a' to 'f'

OctalInteger  := '8#'  OctalDigit  ('_'*  OctalDigit)*

OctalDigit    := '0' to '7'

BinaryInteger := '2#'  BinaryDigit  ( '_'*  BinaryDigit)

BinaryDigit   := '0' | '1'