> For instance, interpreting double-quoted strings differently from what the standard prescribes is not an extension in the sense the standard defines it, but a modification of the standard.
Agreed, but also minor as you can and should set the double_quotes flag, otherwise your program doesn't have portable semantics even among ISO Prolog systems.
> Even though it may sound easy to say "as long as that dialect has a reliable specification and implementation", I know no such system that exists, and what I see from systems that do not adhere to the Prolog standard makes me doubt that such a thing is possible.
Of course it is possible to program against the quirks of a given implementation. That's what you yourself are doing with your CLP libraries. As you note, your main target has different quirks from other targets.
More broadly, Scryer itself demonstrates that it's possible to program against a programming language that doesn't have an ISO standard but does have a good enough specification and an implementation that adheres to that specification.
> The systems that do not follow the standard often have elementary syntactic problems, such as reading a Prolog term that they themselves emit into a different Prolog term, a recipe for disaster and unacceptable in every domain I know.
You're painting with a very broad brush here. What implementations, and what kinds of terms? If your examples involve infix dot, that would be the kind of term nobody uses and nobody should use in modern Prolog, as you well know. Some of these syntactic problems only appear if you go looking for them. Minor syntactic annoyances will be caught in testing.
I agree that such things are bad, but they are knowable, controllable, and quite probably much less relevant in practice than you suggest.
Very very tangentially: The company I work for is very serious about its software supply chains. If we want to use external software for development, we must apply for permission. For that permission, actual programmers and lawyers trawl through the code and licenses and documentation. Scryer's license file lists one copyright holder, and there are many source files without copyright headers, and then there are many source files with copyright headers that name another copyright holder. Our lawyers would not allow us to touch such a system. If you're serious about promoting Scryer as a serious Prolog for serious use, you might want to consider cleaning this up.
Agreed, but also minor as you can and should set the double_quotes flag, otherwise your program doesn't have portable semantics even among ISO Prolog systems.
> Even though it may sound easy to say "as long as that dialect has a reliable specification and implementation", I know no such system that exists, and what I see from systems that do not adhere to the Prolog standard makes me doubt that such a thing is possible.
Of course it is possible to program against the quirks of a given implementation. That's what you yourself are doing with your CLP libraries. As you note, your main target has different quirks from other targets.
More broadly, Scryer itself demonstrates that it's possible to program against a programming language that doesn't have an ISO standard but does have a good enough specification and an implementation that adheres to that specification.
> The systems that do not follow the standard often have elementary syntactic problems, such as reading a Prolog term that they themselves emit into a different Prolog term, a recipe for disaster and unacceptable in every domain I know.
You're painting with a very broad brush here. What implementations, and what kinds of terms? If your examples involve infix dot, that would be the kind of term nobody uses and nobody should use in modern Prolog, as you well know. Some of these syntactic problems only appear if you go looking for them. Minor syntactic annoyances will be caught in testing.
I agree that such things are bad, but they are knowable, controllable, and quite probably much less relevant in practice than you suggest.
Very very tangentially: The company I work for is very serious about its software supply chains. If we want to use external software for development, we must apply for permission. For that permission, actual programmers and lawyers trawl through the code and licenses and documentation. Scryer's license file lists one copyright holder, and there are many source files without copyright headers, and then there are many source files with copyright headers that name another copyright holder. Our lawyers would not allow us to touch such a system. If you're serious about promoting Scryer as a serious Prolog for serious use, you might want to consider cleaning this up.