Lisp as Blub(damienkatz.net)
damienkatz.net
Lisp as Blub
http://damienkatz.net/2008/04/lisp_as_blub.html
6 comments
having Prolog-like syntax without Prolog-like semantics is silly.
Yes. Yes! I'm not the only one thinking it then!
I think the Erlang process model is brilliant but it really took on the ugliness of the Prolog syntax without attaining the full benefits of the Prolog logical semantics.
Yes. Yes! I'm not the only one thinking it then!
I think the Erlang process model is brilliant but it really took on the ugliness of the Prolog syntax without attaining the full benefits of the Prolog logical semantics.
I think Erlang is brilliant because it keeps Prolog's unification (matching) but discards Prolog's backtracking in favor of procedural execution.
Unification can be very useful in solving some problems. Backtracking is also useful but sometimes gets in the way. Procedural code can be used to do anything that any language can do and students are more familiar with it. So I think Erlang is an interesting addition to languages. And that's without considering it's more practical aspects, e.g., multiprocessing, failover capability, etc.
Nor is Prolog syntax particularly ugly. A problem is that it is too simple, so simple that novices can become confused. Brna, Boulay and Pain discuss why Prolog is difficult in the book:
"Learning to Build and Comprehend Complex Information Structures: Prolog as a Case Study" http://www.amazon.com/Learning-Comprehend-Complex-Informatio...
See the review there by Randall Heltzerman titled "The Most Unlikely Book Ever to be Published".
Unification can be very useful in solving some problems. Backtracking is also useful but sometimes gets in the way. Procedural code can be used to do anything that any language can do and students are more familiar with it. So I think Erlang is an interesting addition to languages. And that's without considering it's more practical aspects, e.g., multiprocessing, failover capability, etc.
Nor is Prolog syntax particularly ugly. A problem is that it is too simple, so simple that novices can become confused. Brna, Boulay and Pain discuss why Prolog is difficult in the book:
"Learning to Build and Comprehend Complex Information Structures: Prolog as a Case Study" http://www.amazon.com/Learning-Comprehend-Complex-Informatio...
See the review there by Randall Heltzerman titled "The Most Unlikely Book Ever to be Published".
My misogynistic and politically incorrect, but very accurate, metaphor for erlang is, "The Ugly Girl Who's Great In Bed." You don't mind doing the horizontal polka with her, but she certainly won't win any beauty contests.
That said, a few small changes to the erlang grammar could go a long way towards fixing it (changing separators to terminators, etc). Once you get more familiar with Erlang, you go from writing ugly cascading ifs on multiple conditions to simple clean case statements on tuples. You learn when to use function-clause matching vs. internal matching, etc.
That said, a few small changes to the erlang grammar could go a long way towards fixing it (changing separators to terminators, etc). Once you get more familiar with Erlang, you go from writing ugly cascading ifs on multiple conditions to simple clean case statements on tuples. You learn when to use function-clause matching vs. internal matching, etc.
I think that syntax and semantics are largely orthogonal. When you code in Erlang you just don't think about how the syntax resembles Prolog's.
Also, if you prefer to use Lisp syntax in Erlang you can use LFE (http://groups.google.com/group/erlang-questions/browse_threa...).
Also, if you prefer to use Lisp syntax in Erlang you can use LFE (http://groups.google.com/group/erlang-questions/browse_threa...).
I remember downloading lfe when it first came out, and being stumped at the first step. I've run some simple erlang examples in the past, that's the level of my experience. Is there an article out there to take an erlang newbie by the hand through and provide the compile/load incantations to get to a simple running lfe program?
Without making any sort of general claim, I notice that what I learn in one session of erlang is very easily lost/forgotten. It's like perl in this respect.
And don't tell me the people who object to erlang syntax haven't tried it :) (I say that about people who object to python's indentation) I've tried it. It's extremely hard to keep in one's head, and takes simply too long to become part of 'muscle memory'.
Anyway, pointers to get started would be most appreciated. It's probably counterproductive to my interests to criticize while I ask for help :)
Without making any sort of general claim, I notice that what I learn in one session of erlang is very easily lost/forgotten. It's like perl in this respect.
And don't tell me the people who object to erlang syntax haven't tried it :) (I say that about people who object to python's indentation) I've tried it. It's extremely hard to keep in one's head, and takes simply too long to become part of 'muscle memory'.
Anyway, pointers to get started would be most appreciated. It's probably counterproductive to my interests to criticize while I ask for help :)
I was going to say the same thing. The point he is making (even if true) has nothing to do with the concept of "Blub", and he makes himself look childish by putting it that way. That's too bad. Some of the other stuff I've read by Damien has been solid and I would have expected better.
He just sounds like he was dying to piss on pg's tea party. He ended up just pissing into the wind.
He's reading too much into this. At loads this low, it can't be a language design issue. There's probably just a bug in Mzscheme.
Hard to say whether this post is deliberate linkbait or just overeagerness to see this as evidence confirming a pre-existing bias. Probably a little of both.
Hard to say whether this post is deliberate linkbait or just overeagerness to see this as evidence confirming a pre-existing bias. Probably a little of both.
Confirming bias? Maybe. Link bait? Definitely.
But you say it likes it's a bad thing. Do you think I don't have a valid point? Are you not debugging a memory leak in a production Lisp app?
With Lisp you can put together a site in a few hours. But how many days must later be spent debugging issues like this? Will this time spent debugging be counted against your productivity gains you attribute to Lisp?
This is exactly the sort of problem Erlang has nailed down. And it requires a whole new thinking about program structure. Is it possible you don't see the problems with Lisp because you can't imagine there is a fundamentally better way?
But you say it likes it's a bad thing. Do you think I don't have a valid point? Are you not debugging a memory leak in a production Lisp app?
With Lisp you can put together a site in a few hours. But how many days must later be spent debugging issues like this? Will this time spent debugging be counted against your productivity gains you attribute to Lisp?
This is exactly the sort of problem Erlang has nailed down. And it requires a whole new thinking about program structure. Is it possible you don't see the problems with Lisp because you can't imagine there is a fundamentally better way?
You can't possibly have a valid point, because you're starting from practically zero data. All I have is vague theories about what might be wrong, and what you know about what's going on in our software is a proper subset of what I know.
Why don't you wait till you have more data before wasting all our time with stuff like this? What's the rush?
Why don't you wait till you have more data before wasting all our time with stuff like this? What's the rush?
> Why don't you wait till you have more data before wasting all our time with stuff like this? What's the rush?
I used the opportunity of your reliability failure to make a larger point about reliable software. I admit was deliberately provocative and terse in the posting, but I have futher clarified things in the comments. I thought about writing a long, detailed, well balance article about this. But that wasn't going to happen, I don't have the time. But then I thought why not just write what I think, but not everything I think? So I did.
Sorry, I might be completely wrong about the source of your problems, I am definitely theorizing as to what you are seeing and I don't think I've implied otherwise. But I will say these are the sorts of things that crop up again and again in Java and other GC'd mutable state languages.
Good luck debugging the problem.
I used the opportunity of your reliability failure to make a larger point about reliable software. I admit was deliberately provocative and terse in the posting, but I have futher clarified things in the comments. I thought about writing a long, detailed, well balance article about this. But that wasn't going to happen, I don't have the time. But then I thought why not just write what I think, but not everything I think? So I did.
Sorry, I might be completely wrong about the source of your problems, I am definitely theorizing as to what you are seeing and I don't think I've implied otherwise. But I will say these are the sorts of things that crop up again and again in Java and other GC'd mutable state languages.
Good luck debugging the problem.
A lot of the buzz around Lisp web applications does relate to mutable state accomplished through continuations, but that's not a requisite to using Lisp, nor is it the only advantage to using Lisp.
I manage state via relational databases, and haven't had to deal with any memory-leak bugs. I even found it easy to prevent leaking of database connections.
Mutation is definitely optional. A lot of people even still count Lisp dialects among the functional languages.
I manage state via relational databases, and haven't had to deal with any memory-leak bugs. I even found it easy to prevent leaking of database connections.
Mutation is definitely optional. A lot of people even still count Lisp dialects among the functional languages.
"I used the opportunity of your reliability failure to make a larger point about reliable software."
Your argument construction is not very reliable either. You're basing "large points about reliable software" on... on what exactly? You can't overgeneralize like that, at least not while remaining convincing.
Your argument construction is not very reliable either. You're basing "large points about reliable software" on... on what exactly? You can't overgeneralize like that, at least not while remaining convincing.
It is very possible that Erlang could have a better way than Lisp, and that Lispers can't see it until they learn Erlang. Entirely possible.
But an arbitrary bug in an arbitrary Lisp program is nothing even remotely like sufficient proof for such a statement, unless you are trying to claim that Erlang programs are inherintly bug-free, regardless of how they were implemented...?
But an arbitrary bug in an arbitrary Lisp program is nothing even remotely like sufficient proof for such a statement, unless you are trying to claim that Erlang programs are inherintly bug-free, regardless of how they were implemented...?
> Are you not debugging a memory leak in a production Lisp app?
But, you're confusing the actual application with the Lisp implementation. Arc (and Mzscheme for that matter) are not as mature as Erlang's 20 years (or whatever). If this was running on a more mature Lisp system, I don't think we'd be discussing the same thing.
But, you're confusing the actual application with the Lisp implementation. Arc (and Mzscheme for that matter) are not as mature as Erlang's 20 years (or whatever). If this was running on a more mature Lisp system, I don't think we'd be discussing the same thing.
To be honest, this is not the only such case. Eve Online folks migrated part of their system from SBCL to Erlang for seemingly the same reasons [http://lambda-the-ultimate.org/node/2102].
Having said that, it is still not a language issue, since we have systems such as Termite/Gambit Scheme [http://toute.ca].
Having said that, it is still not a language issue, since we have systems such as Termite/Gambit Scheme [http://toute.ca].
You don't get to pick and choose implementations to compare. Mzscheme was probably chosen because it's a pretty well known scheme implementation and seems popular... likely because it's well done in many ways. But you have to take the bad with the good.
Maybe the problem is Arc's lack of tensile strength.
> But how many days must later be spent debugging issues like this? Will this time spent debugging be counted against your productivity gains you attribute to Lisp? This is exactly the sort of problem Erlang has nailed down.
http://damienkatz.net/2007/12/erlang_vm_crash.html :
"So the Erlang VM died suddenly with a failed memory allocation. This is actually quite okay [...] However, the Erlang VM didn't restart automatically. Apparently we need to configure something for that to happen, only we can't figure out how to make it work. The documentation is either wrong, confusing or the feature is buggy. This is the kind of stuff we keep hitting in Erlang. It's fantastically productive for many tasks, but using some of the built-in libraries and features can be a huge time sink. (inets and xmerl immediately spring to mind)."
http://damienkatz.net/2007/12/erlang_vm_crash.html :
"So the Erlang VM died suddenly with a failed memory allocation. This is actually quite okay [...] However, the Erlang VM didn't restart automatically. Apparently we need to configure something for that to happen, only we can't figure out how to make it work. The documentation is either wrong, confusing or the feature is buggy. This is the kind of stuff we keep hitting in Erlang. It's fantastically productive for many tasks, but using some of the built-in libraries and features can be a huge time sink. (inets and xmerl immediately spring to mind)."
Yes, those things need to be pointed out. I don't want people to think that Erlang is a miracle productivly booster. It's not. The productivity gains are only there in certain application domains, and of course it also require good libraries to support it.
But Erlang to me isn't as much about programmer productivity as it is about reliability. But when building highly reliable systems, of course it's a big productivity boost.
I should point out we've abandoned xmerl (and xml altogether), and things have been much simpler since. We are in the process of moving off the inets http server to mochiweb. Hopefully that will also go smoothly.
But Erlang to me isn't as much about programmer productivity as it is about reliability. But when building highly reliable systems, of course it's a big productivity boost.
I should point out we've abandoned xmerl (and xml altogether), and things have been much simpler since. We are in the process of moving off the inets http server to mochiweb. Hopefully that will also go smoothly.
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It's sort of linkbait, and it'd be more interesting if he had something more substantive to say... however, Erlang certainly is adept at being a robust, stable server, and has had a lot of time and brain power poured into those efforts, so I think they have a right to be proud. It'd be better to find another way of saying it, though.
Tangent: In your troubleshooting, have you already made sure you aren't occasionally receiving a malformed request that is causing the server to puke? In other server software that has displayed that sort of behavior, I've seen that be the problem more often than a traffic issue. I mean; you would have noticed a memory leak type of situation by now, I'd imagine.
I'm pretty sure that isn't the cause, because Patrick has been able to reproduce the problem by generating only correctly formed requests.
I poked around some in news.arc from the download on arclanguage.org; it looks like the newscache macro does quite a lot of heavy lifting... I recall reading someone having some weird issue with the way w/uniq's gensym works (vs. mzscheme's) - is it possible some change has been made to that functionality in the past month or two?
Unless of course Patrick is generating requests that perform functionality, like logging in, up/down voting etc... Then the idea is totally moot since you'd be hitting a much larger cross-section of functionality.
I don't really know Arc and it's intimidating making suggestions knowing the caliber of people looking at the issue; but I figured sometimes an opinion from someone who isn't intimately familiar with the code can be at least a little helpful. If not, feel free to ignore this post completely =D
Unless of course Patrick is generating requests that perform functionality, like logging in, up/down voting etc... Then the idea is totally moot since you'd be hitting a much larger cross-section of functionality.
I don't really know Arc and it's intimidating making suggestions knowing the caliber of people looking at the issue; but I figured sometimes an opinion from someone who isn't intimately familiar with the code can be at least a little helpful. If not, feel free to ignore this post completely =D
have you tried the latest mzscheme? i remember you were running arc on v352, the libraries have changed a lot since then, so maybe the gc did too... iirc there's a patch on anarki or someplace to make it work.
Interesting point about having a process-oriented architecture where each process has its own independent GC, but boy-o-boy is the title a troll-tastic piece of link-bait.
"Why current event X means we should all grind my favorite axe."
It's a pretty robust axe
This guy sounds like a suit in a boardroom . . . just spouting words devoid of validity . . .
If you want to prove something seriously, please find some more examples. (Really!)
To say that Arc is not concerned with brevity or expressiveness is simply ridiculous.
For the record, I think the way Erlang supports functional programming isn't particularly elegant and I think having Prolog-like syntax without Prolog-like semantics is silly.