OpenEuphoria

Re: call_back() etc

• Posted by Roderick Jackson <rjackson at CSIWEB.COM> Aug 12, 1999
• 463 views

noah smith wrote:
>What I've played with so far:
>
>Run ProgA
>    Code
>    system_exec(ProgB)
>    Code
>end ProgA
>
>What I really want to happen is ...

<snip>

>Run ProgA
>    ProgA code
>    Run ProgB
>        Register ProgB functions/procedures with ProgA
>    ProgA code using ProgB functions/procedures
>    end ProgB
>        Unregister ProgB functions/procedures from ProgA
>    ProgA code
>end ProgA

<snip>

I see now. Well, I hate to say it, but to do this the way you're
wanting is pretty much impossible. Once code has been declared in
a context (such as for use with ProgA), you can't get rid of it.

Now you COULD, in theory, do this: write ProgA so that when it
needs to execute ProgB's functions, it runs a second instance of
Euphoria, interpreting ProgB, and gives (as command-line parameters)
the specific function to execute, plus any data needed to get the
right answer.

If you're willing to take the performance hit to run Euphoria for
EACH function call to ProgB, you can do something like the following:

    -- BEGIN PROGB (WARNING: pseudo-code) --

   sequence params, function_name
   object   return_object

   params = get_command_line_params ()
   function_name = params[1]
   params = params[2..length(params)] -- remove the function name

   return_object = call_func (routine_id (function_name), params)

   write_to_file ("temp.txt", return_object)

    -- END PROGB --


    -----------------


    -- BEGIN PROGA --

   function CallProgBFunc (sequence FuncName, sequence ParamStrings)

      sequence ProgBExecString
      object   ReturnObject

      ProgBExecString = "ex progb.ex " & FuncName

      for i = 1 to length (ParamStrings) do
         ProgBExecString = ProgBExecString & " " & ParamStrings[i]
      end for

      system_exec (ProgBExecString) -- you may need system() instead

      ReturnObject = get_data_from_file ("temp.txt") -- pseudo-code

      delete_file ("temp.txt") -- more pseudo-code

      return ReturnObject

   end function

    -- execute some ProgA code...

   x = CallProgBFunc ("square", {sprintf (x)})
   y = CallProgBFunc ("add", {sprintf (x), sprintf (y)})

    -- execute some more ProgA code...

    -- END PROGA --

Now, this method might run into difficulties (I'm not sure if you'll
be able to send sequences to the ProgB functions), but I think it's
pretty close to what you want. If you want to use several ProgB
functions at a time before returning to ProgA, let me know; I still
might be able to help you out.

But honestly, this seems like a lot of work to avoid keeping the
routines in memory, plus the performance hit when using ProgB's
routines is going to be significant. Is there some reason why you
don't want to include code as needed, or at the start? Are you
trying to keep the program size small or something? If there's some
other factor at work here, we might be able to help you get around
it some other way.


Rod