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From: Ruvim <ruvim.pinka@gmail.com>
Newsgroups: comp.lang.forth
Subject: Re: QUIT and ABORT
Date: Mon, 5 May 2025 21:29:19 +0400
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On 2025-05-05 08:11, dxf wrote:
> On 4/05/2025 11:33 pm, Anton Ertl wrote:
>> ...
>> Here's the code I give to the Forth systems:
>>
>> 1 .( a ) cr -56 throw .( b )
>> .s
>> 2 .( a ) cr quit .( b )
>> .s
>> : foo 3 -56 throw ; ' foo catch 5
>> .s
>> : bar 4 quit ; ' bar catch 6
>> .s
>>
>> Let's see what different Forth systems do:
>> ...
> 
> In DX-Forth QUIT is not CATCHable thus -56 THROW simply returns:
> 
>    a
>      THROW #-56
> 
> However modifying it to do so gives these results:
> 
> 1 .( a ) cr -56 throw .( b )
> 
>    'a' is displayed and the stack is: 1

This violates the behavior of `throw` specified in 9.6.1.2275,
because if there is no a user's exception frame, the data stack must be 
emptied.

The table 9.1 in Forth-2012 (or 9.2 in Forth-94) does not affect the 
behavior of `throw` at all.

Your implementation will probably fail the following test case:

   t{ 123 [: 999 -56 throw ;] catch 456 -> 123 -56 456 }t



> 
> 2 .( a ) cr quit .( b )
> 
>    'a' is displayed and the stack is: 2
> 
> : foo 3 -56 throw ; ' foo catch 5
> 
>    stack is: -56 5

These cases are standard-compliant.


> 
> : bar 4 quit ; ' bar catch 6
> 
>    stack is: -56 6
> 

This violates `quit` 6.1.2050, because:
   - `quit` is not allowed to remove anything from the data stack (in 
this case, remove 4 from the stack);
   - `quit` is not allowed to place anything on the data stack (in this 
case, place `-56`);
   - `quit` is not allowed to interpret the remaining part of the input 
buffer  (in this case, interpret "6" and place 6 on the stack).



--
Ruvim