Cute! I normally re-run using the graphical debugger to find out. Maybe we should extend this to show a couple of frames of the stack above the choicepoint? In many cases I do an “up” in the gui tracer to find the call. Should we add it to the debug primitives?

[image] jan: Should we add it to the debug primitives? Can you elaborate? No clear idea comes to mind reading that statement.

Just considering to make it work nicely, e.g., by adding source location and the immediate caller (you often do not need more), invent a good name and add it to the core system just like spy/1, trap/1, etc. An alternative could be to add some key binding to the toplevel you can use after an nondet …

Could the use of identifying the choice points also be used when det/1 is used, the code encounters a choice point when executed and throws an error? The error could be enhanced with the details as prototyped above.

Sound good to me, most especially to add it to plunit when it prints: PL-Unit: Test my_test: Test succeeded with choicepoint That’s where I find it most useful.

For the fun, some progress. To use this, get the latest git version of Prolog as I’ve added a way to get access to the next candidate clause (according to clause indexing) chp.pl (2.3 KB) Some output 109 ?- p, print_chpoint. Warning: Last choice after success r <alt clause> Warning: /home/jan…

Nice! :slightly_smiling_face:The only suggestion I would have is to reword the messages like this: 109 ?- p, print_chpoint. % rename "Warning: Last choice after success r <alt clause>" to Warning: r left a choice point in alternate clause (after success) % rename "Warning: ...chp.pl:7: clause su…

Thanks for the text updates. I think that is better. I wasn’t very happy with the text anyway. Nice to know about this escape sequence. I already hacked something using a plugin in terminator that does this for anything that looks like a filename followed by :Line. That was not very nice tho…

Pushed some stuff that allows for * as a reply to a toplevel answer that will call this. Added the core functionality as print_last_choice_point/0,2 to library(prolog_stack). Adding with unit tests is an exercise to the user :slight_smile:

That is very nice, the ‘*’ in the toplevel result is useful too, good addition. Could you add it to pl_unit when it prints: PL-Unit: Test my_test: Test succeeded with choicepoint ? I think that would be useful too.

Print last choice point - Reply 3 - #10 by jan - General

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