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FigForth Keep script running

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( Display window (stdout) )

                  Demo Keep script running in spite of faults                   

Overview

===
FigForth WARNING set to -1 enables (ABORT) as alternative error
handling. The default for (ABORT) is to perform ABORT but it's
acceptable to replace (ABORT) action with custom user action.  In the
following demo a custom error handling is assigned to (ABORT) by
action of switch settings.  The alternaltive error handling will use
BacForth 'structured cut' to recover from an error (invalid octal
number) and keep the script running.

The _objective_ is to handle errors without halting the script.
Error handling is arranged to log error, make repairs, cease action
of offending script line, and continue running rest of script.
This allows test/demo scripts to include fault handling cases and 
continue on with diagnotics and other cases.

Notes:
i. Fig's BACK is redefined for BacForth BACK TRACKING
i. TCF := Threaded Code Fragment, a BacForth concept
i. BacForth employs only L-stack; I added a C-stack for cut 
   addressing to avoid interactions with L-stack data.
   Being virtual stacks it only cost one cell for the stack
   and a few words for push and pop operations.
===

-- OX ( "octal_number<bl>" -- current_base_number  )
-- Octal number parser. Used to illustrate PRO and CUT actions
: Ox
  PRO            \ push TCF to L-stack
  BASE @ DUP
  R> 2>R         \ rack BASE value
  TMP!           \ save BASE value
  BACK           \ return here on error
  2R> >R BASE !  \ restore BASE
  STATE @ IF     \ snub the compile
  'CUT: TRUE ABORT" Snubbed" ;' EVAL
  ENDIF
  TREK           \ resolve BACK
  CUT:           \ mark BACK for error return
  BL WORD        \ parse octal number
  OCTAL HERE NUMBER DROP [COMPILE] LITERAL
  TMP@ BASE !    \ restore BASE
  CONT           \ control flows to TCF
  ; IMMEDIATE


Setup

sp! decimal
ERESET                      \ default error handling
-uabort                     \ enable user error handling
-ecut                       \ enable cut action
show abort
ABORT status: 
WARNING  -1 
(ABORT)  UABORT 
UABORT    (ERR_DUMP) 
ERRTRACE  Disabled 
ERRCUT    Enabled
--
: boo  ." BOO " 42 . ;      \ some TCF downstream word
: fault 0 ? ;               \ some fault


Interpret

cr i. Ox  644 . boo
 --> 420 BOO 42 
cr i. Ox  755 . boo
 --> 493 BOO 42 
cr i. Ox  644 . Ox 755 . boo
 --> 420 493 BOO 42 
cr i. Ox  644 . hex Ox 755 . boo
 --> 420 1ED BOO 2A 
i. base?  --> 10 
( For unbelievers ) i. BASE @ 1 - . --> 9 
--
-- Three fault cases
--
i. Ox  972  . boo --> 
( continued after fault ) 
i. Ox  644 .  Ox 69 . boo --> 420 
( continued after fault ) 
i. Ox  755 .  fault . boo --> 493 
( continued after fault ) 


Compiled

: FOO Ox 644 . boo ;
i. foo    --> 420 BOO 42 

: BAR hex Ox 49 . boo ;  \ compile fails
' BAR see            \ BAR has been snubbed
BAR 
 134597616 HEX  
 134597620 CUT:  
 134597624 TRUE  
 134597628 0BRANCH  32 ==>  134597664 
 134597636 (")  Snubbed
 134597648 ABORT_MSG  
 134597652 ECR  
 134597656 ERR_ABORTQ  
 134597660 ERROR  
 134597664 ;S  
i. bar               \ snubbed BAR does not halt script --> 
i. base?  --> 10 
( For unbelievers ) i. BASE @ 1 - . --> 9 


Create file

sys [ -f /tmp/foo ] && rm /tmp/foo

"/tmp/foo" Ox 755 FCREATE HCLOSE
i. "ls -og /tmp/foo|cut -c1-10" /sys 1 cuu --> -rwxr-xr-x
sys rm /tmp/foo

"/tmp/foo" Ox 644 FCREATE HCLOSE
i. "ls -og /tmp/foo|cut -c1-10" /sys 1 cuu --> -rw-r--r--

-fin- 

( Command window (errout) )
"ox" /demo 
===
972? 
CURRENT and CONTEXT are WRK    PREVOC is WRK  BASE: 8 
Latest: fault  HERE : 134597572  UNUSED : 11541 
S?: 0 0 134597573 
---  CUTTING
===
69? 
CURRENT and CONTEXT are WRK    PREVOC is WRK  BASE: 8 
Latest: fault  HERE : 134597572  UNUSED : 11541 
S?: 6 0 134597574 
---  CUTTING
===
fault? MEMORY ACCESS FAULT
CURRENT and CONTEXT are WRK    PREVOC is WRK  BASE: 10 
Latest: fault  HERE : 134597572  UNUSED : 11541 
S?: empty 
---  CUTTING
===
49? 
CURRENT and CONTEXT are WRK    PREVOC is WRK  BASE: 8 
Latest: BAR  HERE : 134597620  UNUSED : 11529 
S?: 4 0 134597622 
---  CUTTING

===
bar? ABORTED
CURRENT and CONTEXT are WRK    PREVOC is WRK  BASE: 16 
Latest: BAR  HERE : 134597668  UNUSED : 11517 
S?: 134597640 
---  CUTTING OK

--
me

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FigForth Keep script running sjack@dontemail.me (sjack) - 2026-07-19 16:07 +0000
  Re: FigForth Keep script running albert@SPENARNC.XS4ALL.NL - 2026-07-21 11:20 +0200
  Re: FigForth Keep script running sjack@dontemail.me (sjack) - 2026-07-22 15:25 +0000

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