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Hm, I wouldn't say that conformance to ISO makes a Prolog more "interesting". More useful in certain kinds of applications like the ones you point out, sure. I

Hm, I wouldn't say that conformance to ISO makes a Prolog more "interesting". More useful in certain kinds of applications like the ones you point out, sure. In my experience, there are two Prolog worlds, and that has been true right from the beginning of Prolog with Kowalski coming from the world of pure mathematical formalisms, and Colmerauer coming from the world of pragmatic, practical programmers. The power of Prolog (no pun intended :) comes from the tension between these two worlds. If Kowalski had his way, Prolog would probably be a perfect jewel encased in golden amber, completely unusable but a wonder to behold. If Colmerauer had his way, Prolog would be a quick and dirty programming language fit to replace javascript or C. But they worked together, hand-in-hand, and made something bigger and better and more wonderful than either could have imagined [1]. This duality is also a curse, of course, because its critics can attack it from two sides: it's not pure enough for the purists, not dirty enough for the programmers. Half of its critics complain that it's not 100% declarative, the other half complain that it is not "general purpose" (see elsewhere in this thread). Well, it's not 100% declarative because it's got side-effects, but then what use is a programming language without side-effects? One simply ends up with twisted abominations like monads [2]. And I still don't understand what "general puprose" means, if it doesn't describe Prolog. I think Jan Wielemaker [maintainer of SWI-Prolog] is firmly in the Colmerauer camp, striving to create a language that everybody can use, not just musty academics in their (our!) ivory towers. I have to say I don't always agree with his choices, but I, personally, am infinitely grateful for his oeuvre and I have often considered how little I could have done, for example in my PhD research, without his work. _________________ [1] To hear the French say it of course, it was Colmerauer and Philippe Roussel who created Prolog and Kowalski was probably only visiting Marseilles for unrelated reasons. See the Prolog article on French wikipedia: https://fr.wikipedia.org/wiki/Prolog https://fr.wikipedia.org/wiki/Prolog [2] On the other hand, I think we can both agree that the dynamic database is evil.

dragonwriter 4y ago
> Hm, I wouldn’t say that conformance to ISO makes a Prolog more “interesting”. More useful in certain kinds of applications like the ones you point out, sure. “Interesting” is inherently subjective, and relative specifically to the interests of some specific entity or group. When the Austrian Federal Computing Centre says something is “interesting”, it is shaped by the needs and constraints of the Austrian Federal Computing Centre. What is interesting to you may be different, because you probably have different interests than the Austrian Federal Computing Centre.
jll29 4y ago
Very disingenuous not to even mention Kowalski on the FR Wikipedia entry. In contrast, the English version says: "The language was developed and implemented in Marseille, France, in 1972 by Alain Colmerauer with Philippe Roussel, based on Robert Kowalski's procedural interpretation of Horn clauses at University of Edinburgh."
falsissime 4y ago
> If Colmerauer had his way, Prolog would be a quick and dirty programming language fit to replace javascript or C. No. There are far too many such allusions in this post that it is difficult to dismantle them all. So I will stick to this one. Note that Prolog was born exactly in the very moment when Colmerauer understood how to encode grammars. How much is this quick and dirty? Since Robinson there was some unease about how to encode grammars as this (so far) only lead to extremely inefficient proof procedures. (Roughly, any partition of a text had to be analyzed, most of which were finally discarded) Prior to this moment of understanding in the summer of 1972, as is best illustrated by Philippe Roussel's thesis of May 1972, it was not clear which strategy to use. Quick and dirty features were rather introduced when Prolog was taken from Marseille to Edinburgh. In particular, 1mo, the quite clean error mechanism was replaced by just silent failure. `T =.. L` just failed. Thereby disregarding the observation of Battani and Meloni 1973 that built-in predicates have three possible outcomes: success, failure, and error. 2do, characters were replaced by character codes something any self respecting compiler writer would have never done. But then, all in all, DEC10 Prolog had so many improvements that helped to spread Prolog. Errors are absolutely essential to ensure the correctness of pure Prolog programs. It took some more decades to recover from these quick and dirty setbacks. There is only one single such quick and dirty issue in Prolog I and that is the omission of the occurs check which was present with a flag in Prolog 0 (the first version written in Algol-W). In particular the lame excuse of this omission was started with the Prolog I manual of 1975. It was then mindlessly reiterated time and again to DEC10's and many other systems' manuals. At least, Colmerauer developed thereafter the notion of rational trees present since Prolog II. It is only now that systems slowly recover from this offering an optional occurs check. https://en.wikipedia.org/wiki/Occurs_check#Sound_Unification https://en.wikipedia.org/wiki/Occurs_check#Sound_Unification
- deleted 4y ago
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- YeGoblynQueenne 4y ago
  Thanks for trying to correct me, if I'm wrong (but thanks anyway). What I write is the impression I've formed after reading various sources on the history of Prolog, over the years. Some of them are even by Kowalski himself and my impression that he was the "neat" and Colmerauer the "scruffy" comes from his comments on their relation. I certainly could have misunderstood his comments, or be misremembering them. Unfortunately it will take me some time to dig out the specific sources and check my assumptions [1]. One such recent source is this documentary (in French) about Alain Colmerauer by a lady who shares his surname (a relative, I'm guessing): https://youtu.be/74Ig_QKndvE?t=311 https://youtu.be/74Ig_QKndvE?t=311 I've pointed the link to just before the start of an interview with Kowalski where he says (in English) what I transfer above, that Colmerauer was more practically minded and coming from a computer science side point of view while he (Kowalski) was more theoretically minded and coming from a mathematical logic point of view, and also that this tension created an "alchemy" that would not have transpired otherwise. I watched this documentary very recently and I guess it coloured my comment above. More generally, it's easy to find discussion of the "pure" subset of Prolog and about its purported advantages compared to the rest. I'd have to go back to those textbooks to be sure, but I think I first encountered this idea in The Art of Prolog (O'Keefe) or "The Craft of Prolog" (Sterling & Shapiro), or probably both. And I have heard Ivan Bratko's coding style in his Prolog Programming for AI described as being too imperative and not the recommended style today [2]. I guess what people mean when they talk about "purity" is the lack of side-effects, and other concessions to the everyday needs of the working programmer. I understand the occurs-check flag to be one such concession, for example [3]. So I don't think that all this is just my imagination. In my experience, there really is a divide between Prolog users that think of Prolog as a kind of mathematical notation for computers and smart at the thought of its "dirty" side-effects, and those who just want to use it as a powerful, and beautiful, tool. Like myself. But I should try to be less sentimental in my analysis in the future. Again, thanks for reminding me to check my assumptions and try to remember where my knowledge comes from. _____________ [1] I spent four years during my PhD at Imperial College literally down the corridor from Kowalski's office, but I never had the guts to go and talk to him and ask him about Prolog's history, that I am always very curious about. I regert that now that my PhD is ended and I'm no longer in the same building, or the same city :/ [2] Which is nonsense. Also Bratko said I'm good with Prolog, so there. [3] What does the DEC10 Prolog manual say about the occurs check?

dragonwriter 4y ago

> Hm, I wouldn’t say that conformance to ISO makes a Prolog more “interesting”. More useful in certain kinds of applications like the ones you point out, sure. “Interesting” is inherently subjective, and relative specifically to the interests of some specific entity or group. When the Austrian Federal Computing Centre says something is “interesting”, it is shaped by the needs and constraints of the Austrian Federal Computing Centre. What is interesting to you may be different, because you probably have different interests than the Austrian Federal Computing Centre.

jll29 4y ago

Very disingenuous not to even mention Kowalski on the FR Wikipedia entry. In contrast, the English version says: "The language was developed and implemented in Marseille, France, in 1972 by Alain Colmerauer with Philippe Roussel, based on Robert Kowalski's procedural interpretation of Horn clauses at University of Edinburgh."

falsissime 4y ago

> If Colmerauer had his way, Prolog would be a quick and dirty programming language fit to replace javascript or C. No. There are far too many such allusions in this post that it is difficult to dismantle them all. So I will stick to this one. Note that Prolog was born exactly in the very moment when Colmerauer understood how to encode grammars. How much is this quick and dirty? Since Robinson there was some unease about how to encode grammars as this (so far) only lead to extremely inefficient proof procedures. (Roughly, any partition of a text had to be analyzed, most of which were finally discarded) Prior to this moment of understanding in the summer of 1972, as is best illustrated by Philippe Roussel's thesis of May 1972, it was not clear which strategy to use. Quick and dirty features were rather introduced when Prolog was taken from Marseille to Edinburgh. In particular, 1mo, the quite clean error mechanism was replaced by just silent failure. `T =.. L` just failed. Thereby disregarding the observation of Battani and Meloni 1973 that built-in predicates have three possible outcomes: success, failure, and error. 2do, characters were replaced by character codes something any self respecting compiler writer would have never done. But then, all in all, DEC10 Prolog had so many improvements that helped to spread Prolog. Errors are absolutely essential to ensure the correctness of pure Prolog programs. It took some more decades to recover from these quick and dirty setbacks. There is only one single such quick and dirty issue in Prolog I and that is the omission of the occurs check which was present with a flag in Prolog 0 (the first version written in Algol-W). In particular the lame excuse of this omission was started with the Prolog I manual of 1975. It was then mindlessly reiterated time and again to DEC10's and many other systems' manuals. At least, Colmerauer developed thereafter the notion of rational trees present since Prolog II. It is only now that systems slowly recover from this offering an optional occurs check. https://en.wikipedia.org/wiki/Occurs_check#Sound_Unification https://en.wikipedia.org/wiki/Occurs_check#Sound_Unification

deleted 4y ago
[deleted]
YeGoblynQueenne 4y ago
Thanks for trying to correct me, if I'm wrong (but thanks anyway). What I write is the impression I've formed after reading various sources on the history of Prolog, over the years. Some of them are even by Kowalski himself and my impression that he was the "neat" and Colmerauer the "scruffy" comes from his comments on their relation. I certainly could have misunderstood his comments, or be misremembering them. Unfortunately it will take me some time to dig out the specific sources and check my assumptions [1]. One such recent source is this documentary (in French) about Alain Colmerauer by a lady who shares his surname (a relative, I'm guessing): https://youtu.be/74Ig_QKndvE?t=311 https://youtu.be/74Ig_QKndvE?t=311 I've pointed the link to just before the start of an interview with Kowalski where he says (in English) what I transfer above, that Colmerauer was more practically minded and coming from a computer science side point of view while he (Kowalski) was more theoretically minded and coming from a mathematical logic point of view, and also that this tension created an "alchemy" that would not have transpired otherwise. I watched this documentary very recently and I guess it coloured my comment above. More generally, it's easy to find discussion of the "pure" subset of Prolog and about its purported advantages compared to the rest. I'd have to go back to those textbooks to be sure, but I think I first encountered this idea in The Art of Prolog (O'Keefe) or "The Craft of Prolog" (Sterling & Shapiro), or probably both. And I have heard Ivan Bratko's coding style in his Prolog Programming for AI described as being too imperative and not the recommended style today [2]. I guess what people mean when they talk about "purity" is the lack of side-effects, and other concessions to the everyday needs of the working programmer. I understand the occurs-check flag to be one such concession, for example [3]. So I don't think that all this is just my imagination. In my experience, there really is a divide between Prolog users that think of Prolog as a kind of mathematical notation for computers and smart at the thought of its "dirty" side-effects, and those who just want to use it as a powerful, and beautiful, tool. Like myself. But I should try to be less sentimental in my analysis in the future. Again, thanks for reminding me to check my assumptions and try to remember where my knowledge comes from. _____________ [1] I spent four years during my PhD at Imperial College literally down the corridor from Kowalski's office, but I never had the guts to go and talk to him and ask him about Prolog's history, that I am always very curious about. I regert that now that my PhD is ended and I'm no longer in the same building, or the same city :/ [2] Which is nonsense. Also Bratko said I'm good with Prolog, so there. [3] What does the DEC10 Prolog manual say about the occurs check?