Memory streams about trealla HOT 9 CLOSED

Happy to add something in but I think will be a bit of work. Maybe on the weekend.

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Turns out it was pretty easy to do once I started looking at it. Now providing a SWI-Prolog compatible...

with_output_to(chars(Cs), Goal) :-
	setup_call_cleanup(
		'$capture_output',
		once(Goal),
		'$capture_output_to_chars'(Cs)
	), !.

but you can roll your own without once/1.

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I have added '$capture_error'/0 and '$capture_error_to_chars'/1 to enable capture of user_error. It should be possible now to capture trace info (which goes to stderr) and display in a separate window.

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Much appreciated. The current workarounds are effective so please take your time 🙂

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Excellent! I have one question, more of a Prolog question, but:

query(Query, Status, Output) :-
	%'$capture_output',
	(   call(Query) % ← how can I get this to call $capture_output each time before backtracking?
	*-> Status = success
	;   Status = failure
	),
	'$capture_output_to_chars'(Output).

I can see why SWI shoves the once/1 into there now, haha.
I feel like I am definitely fighting against what you are supposed to do in Prolog, but I'm not sure how to accomplish this otherwise 🤔

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Good point... I tried that but I wasn't able to get it to work 🤔
However, this does work (borrowing a technique from SWI's manual):

js_ask :-
	setup_call_cleanup(
		'$capture_output',
		catch(
			( query(Query, Status, Output) ),
			Error,
			Status = error
		),
		'$capture_output_to_chars'(_) % eat spurious last capture
	)
% ...

query(Query, Status, Output) :-
	(   call(Query)
	*-> Status = success
	;   Status = failure
	),
	'$capture_output_to_chars'(Output),
	( true ; '$capture_output', fail ).

I'm probably just doing something dumb.

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OK I can confirm it is working well. I will integrate it into the WASM stuff soon. Thanks a bunch.
I ran into this issue again: #46 (comment) but still not able to isolate it. Something can trigger the backtracking to work strangely. Capture stuff is good though.
I will make a separate issue for that.

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