a parsing question

From: knotwell@f5.com
Date: Thu May 04 2000 - 16:49:07 MET DST

  • Next message: Jean-Yves Moyen: "Re: a parsing question"

    Hello all--

    I've been writing a configuration file parser using ocaml's lex and
    yacc. So far, I've run into two things (actually they both grow out
    of the same problem) that seem like there should be a better way
    (NOTE: since I'm new the example will seem pretty contrived):

    Let's say I have the following data:
          <yoyo-time>
              40
          </yoyo-time>

    and I want to parse out the 40 and stuff it into a data structure
    usable *outside* of parser (assume lexer.mll, parser.mly, and
    config_test.ml). What I've currently done is the following:

    (* parser.mly *)
    (* NOTE: I tried creating a yoyo_time object, but ocamlyacc
              apparently doesn't like the yoyo_time#set_time syntax *)
    %{
    let yoyo_time = ref 10;;
    let set_yoyo_time newtime = yoyo_time := (int_of_string newtime);;
    %}

    %token YOYO_TIME_BEGIN YOYO_TIME_END INT
    %start <string> main
    %type <string> INT
    %%

    main: YOYO_TIME_BEGIN INT YOYO_TIME_END { set_yoyo_time $2; $2 }
    %%

    =============================

    Unfortunately, I don't know how to "export" yoyo_time to parser.mli.
    My Makefile currently does the following:

        echo "val yoyo_time: int ref" >> parser.mli

    While this works fine, I'd like to avoid using Make as a post-processor.

    I wondered about defining numerous entry points, but I presumed this
    would force me to be extremely careful about the ordering in my config
    file.

    Put another way, am I incorrect in assuming the lexer discards
    previously unmatched data?

    Since this is so long, I'll skip the second question--macros.

    Thanks.
     
    --Brad



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