Date: Mon, 2 Dec 1996 00:56:12 -0700 (MST) From: Ade Barkah <mbarkah@hemi.com> To: terry@lambert.org (Terry Lambert) Cc: hackers@freebsd.org Subject: Re: Lex/Yacc question Message-ID: <199612020756.AAA17064@hemi.com> In-Reply-To: <199611292054.NAA03886@phaeton.artisoft.com> from "Terry Lambert" at Nov 29, 96 01:54:57 pm
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Terry Lambert wrote:
> <ST_HELO>[\r\n] {
> BEGIN INITIAL;
> return HELO_END;
> }
>
> The use of a "HELO_END" token lets us recognize the end of the statement
> for a partial statement (HELO STR_DOMAIN HELO_END is otherwise ambiguous).
You can also avoid states if you want to... for example, in your rfc821.l:
| %{
| #include "y.tab.h"
| %}
|
| %%
|
| helo { return HELO; }
|
| \n { return CR; }
|
| . { return CHAR; }
Then in rfc821.y you can do:
| %token HELO CR CHAR
|
| %start command
|
| %%
|
| command: /* nothing*/
| | command incomplete_helo
| | command helo_command
| { yyerrok; }
| ;
|
| incomplete_helo : HELO CR
| { printf ("Helo requires DOMAIN.\n"); }
|
| helo_command : HELO string CR
| { printf ("Got HELO\n"); /* Do something */ }
|
| string : CHAR
| | string CHAR
(Yea, that CR should probably a CR LF.) I have a hand-crafted rfc821
daemon I use for a custom email-to-paging gateway which I'll probably
rewrite using the above approach. The above code is from a quicky
version I wrote which understands MAIL, RCPT, RSET, QUIT, and DATA.
(Trivial to add.)
Regards,
-Ade Barkah
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