[Caml-list] Calling parser from inside a parser rule

[Caml-list] Calling parser from inside a parser rule

[James Lamanna]

Is it possible to call the parser from inside a parser rule?
For instance lets say I have a grammar rule which accepts
"load [filename]"

Now inside this rule, I want to open the file, and parse all the 
commands in that file using that same parser.

Is there a way to do this?

Thanks.
-- 
James Lamanna

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Re: [Caml-list] Calling parser from inside a parser rule

[Damien Pous]

hi,

why don't you recurse before the parser level ?

lexer.mll:
<<
{ type token = [`Print | `Arf | `Eof] }

let blank = [' ' '\r' '\t' '\n']*
let word = [ 'a'-'z' '.' ]*

rule token = parse
  | blank   { token lexbuf }
  | "#include" blank '"' (word as s) '"' { `Include s }
  | "print" { `Print }
  | "arf"   { `Arf }
      (* ... *) 
  | eof     { `Eof }
>>

reclexer.mll
<<
let token lexbuf: unit -> Lexer.token =
  let acc = ref [lexbuf] in
  let rec aux () = match !acc with
    | [] -> `Eof
    | (x::q) as l -> 
	match Lexer.token x with
	  | `Include s -> acc := (Lexing.from_channel (open_in s))::l; aux()
	  | `Eof -> acc := q; aux()
	  | #Lexer.token as t -> t
  in aux
>>

let t = token (Lexing.from_channel (open_in "toto"));;
t();;
t();;
...

of course you have to handle cyclic includes...

damien

On Sun, 19 Sep 2004 08:50:42 -0700
James Lamanna <jamesl@appliedminds.com> wrote:
> Essentially.
> I want to be able to recurse into my parser.

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Re: [Caml-list] Calling parser from inside a parser rule

[James Lamanna]

On Sat Sep 18 20:52 , skaller <skaller@users.sourceforge.net> sent:

>On Sun, 2004-09-19 at 03:46, James Lamanna wrote:
>> { 
>> let f = open_in $2 in
>> let lexbuf = Lexing.from_channel f in
>> let rec parse_file _ =
>>     try 
>>         List.rev_append (main Lexer.token lexbuf) (parse_file () )
>>     with _ -> []
>> in
>>     parse_file ()
>> }
>> 
>> which obviously doesn't work 
>> because main (the parser main function) isn't defined yet.
>
>Do you mean, how to cope with the lack recursion across
>translation units?
>

Essentially.
I want to be able to recurse into my parser.

Thanks.
--
James Lamanna

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