It became interesting how to read the standard. Formal rules such as BNF, EBNF, Z, ASN.1 do not correlate with the style of presentation in the standard. All the notations that I looked at use either ::= or = as a definition sign, and the standard uses a colon.

 assignment-expression: conditional-expression logical-or-expression assignment-operator assignment-expression throw-expression

Of course, you can rely on common sense, but the standard thing is very formal, which means that there must be a notation for it somewhere.

    1 answer 1

    It uses its own notation, intended for human reading, and not for machine parsing, such as BNF.

    A brief description of the notation is given in the Syntax notation [syntax] section:

    In the syntax of the document, the syntax of the categories used in this document is the syntax.
    There is a list of alternatives to the phrase “one of”.
    The line is indented from the first one.
    An optional terminal or non-terminal symbol is the “opt” [...].