Re: Push parsing from lexer?

Hi Mark,

the third argument is an (optional) token value (which is of type
YYSTYPE -- which corresponds to the Bison %union declaration).

Yours,
Alex
On 14.08.19 18:10, Mark Bannister wrote:
> Hi Alex
> 
> I see my mistake!  I read the docs incorrectly and presumed
> yypush_parse() was taking a function pointer.  Excellent, I think this
> is just what I want.
> 
> So in the example:
> 
> status = yypush_parse(ps, yylex(), NULL);
> 
> I take it that the first argument is yypstate* and the second argument
> is the next token. What is the third argument?  bison.info only appears
> to document a single-argument version (the impure version).
> 
> Thanks,
> Mark
> 
> Sent from Yahoo Mail on Android
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> 
>     On Wed, 14 Aug 2019 at 16:44, Martin Alexander Neumann
>     <[email protected]> wrote:
>     Hi Mark,
> 
>     ah, yypush_parse does not take a pointer to yylex as second parameter,
>     the second parameter is the actual token (you have scanned somewhere
>     else).
> 
>     Yours,
>     Alex
>     On 14.08.19 17:28, Mark Bannister wrote:
>     > Hi Alex
>     >
>     > Thanks for your reply, I had already read up on push parsers before my
>     > posting.
>     >
>     > As you will see from the example on the Push-Decl page, yypush_parse()
>     > takes a pointer to yylex(), so the push parser will call my lexer in
>     > order to get tokens.
>     >
>     > However, if in effect my lexer has the control loop, it already
>     has the
>     > tokens so I would need a way of calling yypush_parse() with a
>     token that
>     > I already have and not require it to make a separate call to yylex().
>     >
>     > Is that possible?
>     >
>     > Best regards
>     > Mark
>     >
>     > Sent from Yahoo Mail on Android
>     >
>     <https://go.onelink.me/107872968?pid=InProduct&c=Global_Internal_YGrowth_AndroidEmailSig__AndroidUsers⁡_wl=ym⁡_sub1=Internal⁡_sub2=Global_YGrowth⁡_sub3=EmailSignature
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>     >
>     >    On Wed, 14 Aug 2019 at 16:02, Martin Alexander Neumann
>     >    <[email protected] <mailto:[email protected]>> wrote:
>     >    Hi Mark,
>     >
>     >    please have a look at instructing Bison to generate a push parser
>     >    instead of a pull parser (which is the default):
>     >
>     >    https://www.gnu.org/software/bison/manual/html_node/Push-Decl.html
>     >
>     >    Yours,
>     >    Alex
>     >
>     >    On 14.08.19 09:14, Mark Bannister via help-bison wrote:
>     >    > I am writing a Bison re-entrant push parser with my own lexical
>     >    analyser.  However, if my understanding is correct, the only way I
>     >    know to make this work is a bit inefficient.
>     >    > I have a debugger interface that I'm developing that takes one
>     >    line of input at a time.  The debugger then decides which language
>     >    module to call based on a simple pattern match.  It invokes an
>     >    entry-point in the correct module with the line of input it has
>     >    received.  Only one of the language modules will use bison, the
>     >    other interfaces are too simple to need it.  Once I am in the
>     >    language module I am scanning for tokens and some simple context. 
>     >    For example, it's possible to call out to another language module
>     >    from here too so this loop cannot be implemented in bison as the
>     >    full grammar cannot be defined at this point. Also, the syntax
>     >    structure may be varied depending on the value of a variable, and
>     >    this affects whether or not a complete statement is or is not
>     >    terminated by semicolons, for example.
>     >    > What I would like to do is call my bison parser for each token
>     >    that I collect in the main loop of my language module, and from
>     >    there I can create an AST.  So, for example, I would go:
>     >    > Debugger -> Module Loop -> Bison (per token) -> AST
>     >    > This obviously requires a push parser, but the problem I am
>     facing
>     >    - and the reason for my call for help - is that bison wants to call
>     >    a lexer even though I already have the token I need to push to it. 
>     >    So it appears to be back-to-front.  The only way I can think of
>     >    right now to solve the problem is to store my token in a structure
>     >    that I pass by reference to bison, which it passes to a lexer
>     >    function that just extracts the details and returns it back to
>     >    bison.  I think this should work but it is suboptimal and looks
>     like
>     >    this:
>     >    > Debugger -> Module Loop -> Bison (per token) -> lexer (return
>     >    token) -> Bison -> AST
>     >    > Is there a better way?
>     >    > Best regardsMark
>     >    >
>     >    > Sent from Yahoo Mail on Android
>     >
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> 
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>     >
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>     >
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