Re: How to write the BNF

[Sharan Basappa]

Thanks. On the last part, I believe the keywords would also be
generally categorized as tokens/terminals.
Suppose I have come up with a new language and want to give a formal
explanation to it.
For items like if, else, main I categorize them as keywords and then I
categorize
if, else, main, {, } as terminal tokens. Do you think this is a good
way of explaining the
language

On Tue, Mar 11, 2008 at 2:35 PM, Hans Aberg <address@hidden> wrote:
>
>  On 10 Mar 2008, at 15:55, Sharan Basappa wrote:
>
>  > I would like to know how to write BNF for code blocks that have
>  > optional block enclosing symbols like {}
>  > For example, the following statements are both valid:
>  >
>  > if () $printf();
>  >
>  > if()
>  > {
>  >   func1;
>  >   func2;
>  > }
>  >
>  > How to I specify that {} are optional when number of statement is
>  > just one.
>
>  One way to do it, is to write it as EBNF, and then use rewrite rules
>  to BNF. Search for "EBNF" here
>    http://lists.gnu.org/pipermail/bug-bison
>
>  Or directly
>    AorNone:
>         /* empty */
>      | A
>  The empty expansion has no token - I just put in a comment for
>  clarification. Also see the Bison manual.
>
>
>  > Also, when I write a BNF for a new lanugage, the words that are
>  > reserved are categorized as keywords.
>  > What about symbols like {} etc. What are they categorized as?
>
>  In Bison, they are called "tokens", "terminals, or "grammar
>  constants". This includes also defined variables and such -
>  everything that comes directly from the lexer (generated by say
>  Flex). Bison parses only tokens.
>
>    Hans Aberg
>
>
>