Re: EVALUATE in Callback Revisited

Bob,

> : test-word 5 5 + = ;

It appears you are attempting to compile a definition which opens up a
whole can of worms. I tackled this problem while developing a Forth
Script engine for our Forth Web Server. I modified it (below) for
EVALUATE (untested - sorry).

Good luck,
Mike

50000 VALUE /SCRIPT-DICT \ How much code space to ALLOCATE

: INIT-FORTH-SCRIPT ( -- )
   DECIMAL /FORTH POSTPONE [
   0 ( =keybrd ) 'SOURCE-ID !
   CASE-INSENSITIVE BLK OFF WARNING OFF
   ['] (COMPILE,) IS COMPILE,
   ['] (SOURCE) IS SOURCE
   ['] DROP IS >XREF ;

: EVAL-SCRIPT ( addr len -- )
   SAVE-INPUT N>R
   INIT-FORTH-SCRIPT
   'REMEMBER OFF 'PRUNE OFF ( Initialize Prune/Remember )
   H @ >R HLIM @ >R
   /SCRIPT-DICT ALLOCATE THROW
   DUP >R DUP H ! /SCRIPT-DICT + HLIM ! ( create "new" dictionary
space )
   S" MARKER FORGET-SCRIPT" ['] EVALUATE CATCH ?DUP
   IF >R ( Stash ior )
   ELSE INIT-FORTH-SCRIPT
      ( addr len ) ['] EVALUATE CATCH ( ior ) DUP >R
      IF 2DROP ( addr & len ) THEN
      INIT-FORTH-SCRIPT
      S" FORGET-SCRIPT" ['] EVALUATE CATCH
      IF 2DROP ( eval string+len ) THEN
   THEN R> ( ior ) ( cleanup )
   R> FREE THROW
   R> HLIM ! R> H ! ( restore dictionary )
   NR> RESTORE-INPUT DROP
   ( ior ) THROW ;

-----Original Message-----
From: sftalk-bounce_at_forth.com [mailto:sftalk-bounce_at_forth.com]On
Behalf
Of Bob Nash
Sent: Wednesday, June 18, 2003 2:13 PM
To: sftalk
Subject: [sftalk] EVALUATE in Callback Revisited

Some time ago (September 2001 and June 2002) there were discussions =
about using EVALUATE in a callback as part of a turnkeyed app.

According to Rick, the problem is that internal variables and system =
state are not initialized during callbacks, so the search order and =
CONTEXT had to be set before executing EVALUATE in the callback.

There were two solutions. One (from Rick) was to define the callback
=
word something like this:

: EVAL DECIMAL ONLY FORTH POSTPONE [ Buffer ZCOUNT ['] MY-EVALUATE =
CATCH IF 2DROP THEN ;

Buffer contained the string to be evaluated and MY-EVALUATE was a =
version of EVALUATE that did not try to write errors to the console.

Another solution (again from Rick) was to execute a special word, =
INHERIT-SEARCHORDER, just before executing the callback switch =
statements:

: INHERIT-SEARCHORDER OPERATOR #ORDER HIS #ORDER #VOCS 3 + CELLS
CMOVE =
; \ I'll trust Rick on this one!

I just tried various combos of the above with no success (mostly I got
a =
DOS console window that persisted for a while and then went away).
The =
evaluated words were simple stack manipulations like : test-word 5 5
+ =
; The word didn't seem to execute (nothing on the stack).

Finally, my questions:=20

1. Did anyone get this to work? =20
2. Do you have code snippets you are willing to share?

This is just for my own edification -- no immediate need. Thanks!

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Received on Wed Jun 18 2003 - 17:18:29 PDT