Hi Everyone,
This is my first post on this mailing-list. Nice to meet you all! I was just wondering whether someone could point me in the right direction for a Prolog problem I'm struggling with at the moment.
The situation is thus. I am currently starting to develop a Prolog metainterpreter as part of a university project to produce a Prolog teaching aid for new learners of Prolog, somewhat in the form of a better, more visual and user-friendly debugger (as opposed to the rather obtuse default text-based one). I have attached a first try at a basic interpreter. However, there is a few quite important issues I would like to solve. Firstly, there is a big problem with examining system-defined predicates, as it seems that we have to declare any predicate which we use 'clause/3' on as
dynamic before we can examine it, and the interpreter refuses to call clause on any system-defined ones. Is there a way to get round this problem (in order to have a more general interpreter which can work with any predicate)? Or is it just something I'll have to live with? Secondly, the way the system is envisioned to work at the moment is very much by first calling the Prolog proof ( via using prove(... goal ...) predicate ) and producing some information (such as the recursive call trace and success/fail information in the current version), and then after the first pass examining the results and using the data to produce further illuminating information about the predicate being proved in a suitable form. However, this process can only be forward-moving (though using the information I can create something which allows stepping backwards/forwards through the proof, as a seperate process) . I'd like to know whether it is
actually possible to step 'back-up' (ie. undo) a proof step in real time as part of the actual Prolog system, or whether we can move only in a forward direction?
And thirdly, what are 'frames', and what are they used for? Is this something I could be using to obtain hooks into the Prolog proof process? If so could someone point me to a tutorial or something to enable me to understand better about them (as from reading just the API description I didn't really get what was going on with these and how to use them).
Many Thanks in advance!
Huayi Huang
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