52 lines
1.2 KiB
Forth
52 lines
1.2 KiB
Forth
There are people who consider `abort` to be the most
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fundamental building block in writing programs. For
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them, it is not just a debugging tool.
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~~~
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:s:shout (s-) '!_ s:prepend s:put nl 'Stack_:_ s:put dump-stack nl ;
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{{
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'Depth var
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:message (-) 'abort_with_trail_invoked s:shout nl
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'Do__reset__to_clear_stack. s:put nl ;
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:put-name (a-) fetch d:lookup-xt
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dup n:-zero? [ d:name s:put nl ] [ drop ] choose ;
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---reveal---
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:trail repeat pop put-name again ;
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:abort (-?) depth !Depth message trail ;
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:s:abort (s-) 's:abort_:_ s:prepend s:put nl abort ;
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}}
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~~~
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`trail` leaves garbage on the stack.
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This garbage is difficult to shake off since `trail`
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destroys the contents of the return stack. The easiest
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way I have found so far is to `reset` manually.
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To test, run the following code interactively:
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```
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:a 'aaa s:abort ;
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:b a ;
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:c b ;
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c
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reset
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```
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## assert
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~~~
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:assert (q-) call [ abort ] -if ;
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:assert.verbous (q-) call [ 'assert_:_fail s:abort ] -if ;
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~~~
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If `0;` is invoked with an empty stack, it fails and
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kills the session.
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```
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:t 'before_ s:put 0; 'after s:put nl ;
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'#0_t_nl_#1_t_nl s:evaluate
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'reset_t s:evaluate (--_kills_session
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```
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If this is dangerous, place an assertion before `0;` .
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