Re: QUIT and ABORT

On 2025-05-16 12:19, dxf wrote:

On 16/05/2025 3:53 pm, Ruvim wrote:

On 2025-05-15 06:14, dxf wrote:

...
>
CATCH has already done the damage.  It would be naive for a programmer
to assume he can re-throw QUIT and it will be as if nothing ever happened.

>
My point is that such a word is completely useless.

 The goal is catching fish.  What happens to the ones you catch and then
decide to throw it back in is relatively minor.  If they end up a bit
worse for wear that's just how it is.

Could you please provide a practical use case for this? The standard `quit` is useful for debugging, at the least.
If your goal is to catch `quit` in your program, just redefine `quit` accordingly. Then, of course, the system is not a standard Forth system after loading your program (see 4.2.2).

Presumably an implementer of a catchable QUIT actually wants it caught.
The question then is what can he do for the occasions when he wants it
impervious to CATCH and there are solutions for that.
>

>
What solution do you mean?

 Default behaviour of QUIT is Core QUIT.  THROW handles -56 by jumping to
Core QUIT.

If you make `throw` do this regardless of whether a user's exception frame exists in the exception stack, you make the `-56` error code uncatchable. So, the following test case will fail:
   t{  [: -56 throw ;] catch -> -56 }t
And what is the benefit?

 The application programmer then has the option of making QUIT
catchable by defining:
    : QUIT -56 THROW ;
 

But this option already exists. There is no need to specially handle `-56` in `throw`.
--
Ruvim