Lexical overview
================

+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  small-letter           |    →    |    ‘a’ \| ‘b’ \| ... \| ‘z’                                                                                                                            |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  cap-letter             |    →    |    ‘A’ \| ‘B’ \| ... \| ‘Z’                                                                                                                            |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  letter                 |    →    |    small-letter \| cap-letter                                                                                                                          |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  identifier             |    →    |    (small-letter \| ‘_’) {letter \| digit \| ‘_’}                                                                                                      |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  small-keyword          |    →    |    identifier ‘:’                                                                                                                                      |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  cap-keyword            |    →    |    cap-letter {letter \| digit \| ‘_’} ‘:’                                                                                                             |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  argument-name          |    →    |    ‘:’ identifier                                                                                                                                      |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  op-char                |    →    |    ‘!’ \| ‘@’ \| ‘\#’ \| ‘$’ \| ‘%’ \| ‘^’ \| ‘&’ \| ‘*’ \| ‘-’ \| ‘+’ \| ‘=’ \| ‘~’ \| ‘/’ \| ‘?’ \| ‘<’ \| ‘>’ \| ‘,’ \| ‘;’ \| ‘\|’ \| ‘‘’ \| ‘\\’  |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  operator               |    →    |    op-char {op-char}                                                                                                                                   |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  number                 |    →    |    [ ‘-’ ] (integer \| real)                                                                                                                           |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  integer                |    →    |    [base] general-digit {general-digit}                                                                                                                |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  real                   |    →    |    fixed-point \| float                                                                                                                                |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  fixed-point            |    →    |    decimal ‘.’ decimal                                                                                                                                 |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  float                  |    →    |    decimal [ ‘.’ decimal ] (‘e’ \| ‘E’) [ ‘+’ \| ‘-’ ] decimal                                                                                         |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  general-digit          |    →    |    digit \| letter                                                                                                                                     |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  decimal                |    →    |    digit {digit}                                                                                                                                       |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  base                   |    →    |    decimal (‘r’ \| ‘R’)                                                                                                                                |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  string                 |    →    |    ‘’’ { normal-char \| escape-char } ‘’’                                                                                                              |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  normal-char            |    →    |    any character except ‘\\’ and ‘’’                                                                                                                   |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  escape-char            |    →    |    ‘\\t’ \| ‘\\b’ \| ‘\\n’ \| ‘\\f’ \| ‘\\r’ \| ‘\\v’ \| ‘\\a’ \| ‘\\0’ \| ‘\\\\’ \| ‘\\’’ \| ‘\\"’ \| ‘\\?’ \| numeric-escape                         |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  numeric-escape         |    →    |    ‘\\x’ general-digit general-digit \| ( ‘\\d’ \| ‘\\o’ ) digit digit digit                                                                           |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  comment                |    →    |    ‘"’ { comment-char } ‘"’                                                                                                                            |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
|  comment-char           |    →    |    any character but ‘"’                                                                                                                               |
+-------------------------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------+