From Newsgroup: comp.lang.forth

Toad doesn't have CATCH/THROW but FigForth provides user abort (ABORT) .
Have BacForth type words in RTC vocabulary. Using BACK...TREK and
CUT: ... -CUT made SNAPSHOT error handler to show stacks and return
to cleanup code marked by CUT: . Not nearly as capable and slick as CATCH/THROW but adequate for my light-weight applications.

Have CATCH/THROW in Frog but Toad is all about making full use of
FigForth facilities (use of abundant vocabularies has been very
entertaining, ain't KISS.)

User abort with cut: ... -cut



Some code

-- SNAPSHOT
-- User abort action
-- dump data stack and top of return stack
-- (return stack top holds the address of the word where the
-- fault was detected. )
-- Process each cut: cleanup location
: SNAPSHOT
RTC
BEGIN
-CUT
cr ." --- (!) User abort: "
cr ." Data stack: " s? xx
cr ." Return : " r .
cr ." --."
cr
LDEPTH 0= UNTIL
cr ;

-- YO
-- Display some items of interest
: YO
rtc
cr ." L-stack depth: " ldepth .
cr ." LP : " lp@ . tab lp@ @ .
+voc
cr ." (ABORT) : " ' (ABORT) @ CELL+ NFA ID.
cr ." UABORT : " dfa' uabort @ CELL+ NFA ID.
cr ." FDIID : " fdiid . \ file id, zero after cleanup
cr
;


Success example

"pad/txt" svdir sv! \ assign input path prefix
' snapshot is uabort \ assign user abort
-uabort \ enable user abort
-pause \ allow pausing
fviews -p rubyatXLIX rubyatLI; \ view two files with pause option

pad/txt/rubyatLI:

LI.
The Moving Finger writes; and, having writ,
Moves on: nor all thy Piety nor Wit
Shall lure it back to cancel half a Line,
Nor all thy Tears wash out a Word of it.

-more-

pad/txt/rubyatXLIX:

XLIX.
Tis all a Chequer-board of Nights and Days,
Where Destiny with Men for Pieces plays:
Hither and thither moves, and mates, and slays,
And one by one back in the Closet lays.
+uabort \ disable user abort
yo \ look at items of interest
L-stack depth: 0
LP : 134566380 -1
(ABORT) : ABORT
UABORT : SNAPSHOT
FDIID : 0

..CURRENT and CONTEXT are WRK BASE: 10 Latest: YO


Fail example

-uabort
fviews rubyatXLIX foo rubyatLI; \ foo doesn't exit, should fail

pad/txt/rubyatLI:

LI.
The Moving Finger writes; and, having writ,
Moves on: nor all thy Piety nor Wit
Shall lure it back to cancel half a Line,
Nor all thy Tears wash out a Word of it.


pad/txt/foo:

--- (!) User abort:
Data stack: 134583709 10 134582004 -2 666
Return : 134581372
--.

--- (!) User abort:
Data stack: empty
Return : 134582140
--.

--- (!) FVIEWS abandon
+uabort
yo
L-stack depth: 0
LP : 134566380 -1
(ABORT) : ABORT
UABORT : SNAPSHOT
FDIID : 0

..CURRENT and CONTEXT are WRK BASE: 10 Latest: YO


-fin-
OK
--
me
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From Newsgroup: comp.lang.forth

Ha,ha. Fooled myself looking at file id (FDIID) for zero value to
indicate cleanup took place. When file i/o failed because file foo
didn't exist, FDIID never got set so was always zero. (there were
other means of verifying that cleanup code got accessed, e.g. the
"FVIEWS abandon' being printed.
But to see FDIID being reset I needed to at least get the file opened
and then have it fail. So just open a corrupt file. No! Whatever I
put into a file, nulls and control characters, does not make the i/o
fail! To have failure has to be done on my end in processing the
data. So patched UABORT into a low level part that was acting
on the data. Mission achomplished.
--
me
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