This is half a question and half me sharing what I already found out. In short: when exchanging Prolog terms (in text form) with a different Prolog system or other software that reads Prolog terms, how do I make SWI-Prolog write terms so that the other side has the best chance of understanding them? …

It seems you figured out most of it. SWI-Prolog writes lists as [a,b,c] because of its different internal representation. There is another huge advantage though. Using .(a,.(b,.(c,[]))) has the huge disadvantage that you cannot reduce any of these terms before you get the first ) because they m…

[image] dgelessus: braces ( {x} instead of {}(x) ). The {...} notation seems to be forgotten in almost every Prolog system’s documentation – I remember being surprised by it in Quintus Prolog decades ago when I inadvertently used {...} outside of a DCG, and later in SWI-Prolog when I wrote a …

One possibly confusing thing is that {...} takes a single term and commas inside it are operators. So, novices might think that {a,b} is the same as '{}'(a,b) but it’s actually '{}'((a,b) or '{}'(','(a,b)). (I’ve seen novices write things like (a,b,c), not realizing that this is equivalent to ','(a…

[image] jan: I doubt {a} was intentionally written such. At least with write_term/2, this seems to be intentional, according to this footnote from the docs: In traditional systems this flag also stops the syntactic sugar notation for lists and brace terms. In SWI-Prolog, these are controlle…

[image] peter.ludemann: Another possibility for interoperationality is to implement library(fastrw) at the receiving end, which will have the additional advantage of speed-up for large terms. Our code actually has some fastrw support already, precisely because of the improved performance. But…

[image] dgelessus: But in write_canonical/1 it doesn’t really make sense - unlike with lists, the brace syntax doesn’t hide a non-traditional term format that would cause problems with other systems. Right. Some digging in the history shows the introduction of the brace_terms option without…

Speaking of dicts, what should write_canonical/1 do? If the intent is interoperability, it might be nice to have a iso_only option, to prevent surprises if the code happens to output SWI-Prolog syntactic extensions. I don’t know. Interoperability is a nightmare. I guess atoms can only be safely…

[image] jan: Interoperability is a nightmare You can always use protobufs. :grimacing: That even allows exchanging data with C++, Python, Java, etc. although I expect performance would be worse than write_canonical/1 and read/1. General interoperability is, as you say, a nightmare. You’d pr…

Jan W. has several patches related to this topic. Note: The list is based on dates and not the exact commits. [image] Commits · SWI-Prolog/swipl-devel Main development repository. Contribute to SWI-Prolog/swipl-devel development by creating an account on GitHub. …

[image] peter.ludemann: Nobody seems to have got very far with a comprehensive type system for Prolog terms I wouldn’t say that. Most of the type systems did come up with typing terms AFAIK. Some probably have numeric ranges. I doubt one has dealt with atom content such as allowed chara…

Best way to write terms for interoperability

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Best way to write terms for interoperability

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