How to handle errors in general and in the Prolog world is high up on my list of things to figure out, and the discussion is a great jump off point for this [1]. More specifically, I wonder what client code should expect from a predicate to return true of false only, and when client code is also ex…

There’s also a discussion here: [image] Errors considered harmful Request For Comments Interesting discussion on Picat extensions and cuts and I’d like to add my own personal pet peeve with “standard” Prolog. I don’t think there would be much opposition to the topic title…

In my mind there are only two categories: failure you expect, and failure you didn’t expect. The latter is a bug if it occurs, because you should have anticipated it. So if you expect a failure to occur, then when it occurs you decide what to do: pass the failure up; throw; try an alternate soluti…

[image] abaljeu: t. So if you expect a failure to occur, then when it occurs you decide what to do: pass the failure up; throw; try an alternate solution. Thank you for your insights. It seems to me that there is an additional category of failures such as when a precondition fails – in partic…

[image] grossdan: failures such as when a precondition fails Can these be implemented by adding assertion/1 goals to a clause? (That is, not limited to type checks, but to other preconditions, such as “non-negative integer” or “is a balanced red-black tree”) And if you have pre-conditions, I…

There is a book, Elements of Programming by Stepanov and McJones (try to ignore the C++ connection). This book makes heavy use of preconditions. What those are is already explained in the first section (page 13). What I find curious is that the authors give a formal description of what preconditions…

re: assertion/1 I decided to use the predicates provided by the error library to raise type, domain and other errors – so, indeed its not only about type checking. Also, i wrapped it all into term_expansion so that these checks can be selectively enabled during development and disabled during depl…

It seems to me that I concur with your view and appreciate they way you phrased it (“refuse to incorporate exceptions in the control flow”). Although, as mentioned, in rare occasions i found doing just that – because the exception based control flow made most sense

[image] grossdan: wrapped it all into term_expansion so that these checks can be selectively enabled during development and disabled during deployment wrap_predicate/4 can be used instead of term_expansion. (The rdet pack was changed from using term_expansion to using wrap_predicate/4, result…

Best Practice for Error handing

Discussion

peter.ludemann October 14, 2021, 6:15pm 2

There’s also a discussion here:

Topic		Replies	Views
Best practice for catch/3 with multiple possible errors? Predicate how-to	17	2509	October 17, 2021
Errors considered harmful Request For Comments	106	5912	August 8, 2021
When does assert fail? Running out of space? Help!	67	2836	January 6, 2020
Best practices for throw(...)? Predicate	3	630	September 26, 2020
Catch / throw example with custom error Help!	3	1281	February 17, 2019

Best Practice for Error handing

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