Why Lazy Functional Programming Languages Rule 439
Da Massive writes "Techworld has an in-depth chat with Simon Peyton-Jones about the development of Haskell and his philosophy of do one thing, and do it well. Peyton-Jones describes his interest in lazy functional programming languages, and chats about their increasing relevance in a world with rapidly increasing multi-core CPUs and clusters. 'I think Haskell is increasingly well placed for this multi-core stuff, as I think people are increasingly going to look to languages like Haskell and say 'oh, that's where we can get some good ideas at least', whether or not it's the actual language or concrete syntax that they adopt.'"
I would have RTFA (Score:5, Funny)
But I was too lazy to click on 13 pageviews.
Mmmm, Kay. (Score:4, Informative)
Hascal, and other functional languages may be good for multi-core development. However not to many programmers program in them... Plus I find they do not scale well for larger application. Its good for true computing problem solving. But today most developopment is for larger application which doesn't necessarly solve problems per-say but create a tool that people can use.
Re:Mmmm, Kay. (Score:5, Insightful)
I spent a whole term at uni learning Miranda, which is similar to Haskell, I really liked it. I have *never* seen it being used since. To my mind they both belong in the category 'interesting, but pointless'.
Its not just because they're old. If age was what killed languages, C and Lisp would be long dead. There just isn't anything I could do with either that I wouldn't be able to do more easily with another more 'mainstream' language.
Re:Mmmm, Kay. (Score:4, Interesting)
I call FUD. There's a lot of things that Lazy functional languages make easy, that mainstream languages don't. Here's just a few examples:
Infinite data structures can be handled naturally. Here's a function that generates the infinite list of fibbonacci numbers:
fibs x y = x : (fibs y (x + y))
Here's a list that does a complex calculation on every one of the fibbonacci numbers:
map complexCalculation (fibs 1 1)
While we're at it, Haskell programs are very easily parallelisable. Here's the same list, but computed on multiple cores:
(parMap rnf) complexCalculation (fibs 1 1)
Haskell only evaluates what it has to -- this program for example which looks up the 3000th element of the sequence will not compute the complexCalculation on the 2999 fibbonaccis before hand like a traditional program would:
(parMap rnf) complexCalculation (fibs 1 1) !! 3000
There's only a small sample of what's so powerful about these languages. If you'd bothered to RTFA, you'd know there are a lot more. But then, I guess this is slashdot.
Re:Mmmm, Kay. (Score:5, Insightful)
I call FUD. There's a lot of things that Lazy functional languages make easy, that mainstream languages don't. Here's just a few examples: Infinite data structures can be handled naturally.
Might that be because infinite data structures don't often exist in mainstream and/or commercial software applications?
Re:Mmmm, Kay. (Score:5, Insightful)
Might that be because infinite data structures don't often exist in mainstream and/or commercial software applications?
Might that be because mainstream programming languages don't support infinite data structures?
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Yup, lazy, functionnal, imperative, object : for each problem there is a better solution. However maybe there would be at then end a language where :
1) syntax could be made a little less strange so that people knowing C (like python by example and then adding its own concepts) could make simple things, simply
2) different paradigms should be coexisting peacefully - fast, simple inner loops in C, structured, object in ($dynamic language), algorithms needing such kind of concurrency or metaprogramming, possible also.
3) a pony
Can't help you with #3. I've been thinking about solutions to #2 (Integration between languages is still a real weak point... I hope this will change over time - part of that will be increased cooperation between the tools themselves. Seems like Microsoft has taken a decent stab at this with .NET...)
I don't really agree with #1. I don't believe any language yet (especially not C++) has "the perfect syntax", so when it comes to defining new languages I don't believe emulation (of syntax) is necessarily t
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Sure they do. How many lines in the next web page? How many variables? How many on the whole site? How many simultaneous users? How many files do they need access to?
Not having to worry about these constraints saves tons of time.
Re:Mmmm, Kay. (Score:5, Insightful)
Might that be because infinite data structures don't often exist in mainstream and/or commercial software applications?
Sure they do. On my computer, there's an infinite stream of ethernet frames arriving, an infinite stream of video frames leaving, an infinite stream of keyboard events arriving, etc.
The thing about functional languages, and strict lazy functional languages like Haskell, is that the underlying principles are quite different from procedural languages like C. In C, you tell the computer to do things. In Haskell, you tell the computer the relationships between things, and it figures out what to do all on its own.
Personally, I suck at Haskell --- I'm too much of a procedural programmer. My mind's stuck in the rails of doing thing procedurally. But I'd very much like to learn it more, *because* it will teach me different ways of thinking about problems. If I can think of an ethernet router as a mapping between an input and output stream of packets rather than as a sequence of discrete events that get processed sequentially, then it may well encourage me to solve the problem in a some better way.
Re:Mmmm, Kay. (Score:4, Informative)
On my computer, there's an infinite stream of ethernet frames arriving, an infinite stream of video frames leaving, an infinite stream of keyboard events arriving, etc.
You keep on using that word. I do not think it means what you think it means.
Re:Mmmm, Kay. (Score:5, Interesting)
When the last argument given is "look it up", I suspect there's no counter-argument.
In what way is there an "infinite stream of ethernet frames ariving" on your computer with its finite lifetime?
If you have an explanation, why not give it?
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Well, in this case the "infinite stream" is really a stream of indefinite size. However, you can treat it as being infinite.
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we don't usually have wires with infinite bandwidth, disks capable of storing infinite frames of video, or users that can press infinite keys.
You completly missed the point. An infinite data structure in a lazy language isn't something that you write down to disk or something you store in memory, its a concept with which you structure your code. For example instead of having a while-loop to poll an event from an event queue like you would do in C, you could have an infinite list of all the events that you system would ever create, but it isn't a list/array in the C sense, its much more like a generator in Python in that the elements are only gene
Re:Mmmm, Kay. (Score:5, Insightful)
Re:Mmmm, Kay. (Score:5, Informative)
Absolutely, and this is why there's one of freenode's biggest IRC channels, a pair of mailing lists with thousands of subscribers, and the Hackage [haskell.org] library/tool repository just waiting to help you solve your real world problem. Be it Compiler building [haskell.org], version control [darcs.net], writing interpretters for popular imperrative languages [perlfoundation.org], Writing 3D shooters [haskell.org], or a whole host of other tasks.
Re:Mmmm, Kay. (Score:5, Insightful)
I call meme misuse.
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I call meme misuse.
Thank you. There is no fear, uncertainty, or doubt here.
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Mmmm... yes, I see you picked a few practical, real world examples, and didn't try to stack the deck with tasks that Haskell (or a similar language) would be particularly well-suited for.
Or not.
Re:Mmmm, Kay. (Score:5, Insightful)
Here's a function that generates the infinite list of fibbonacci numbers: fibs x y = x : (fibs y (x + y))
You have just demonstrated thermian's point.
How often do you actually need to generate infinite sequences? I have never needed to do that outside of a functional programming class.
I'm a big fan of alternative programming languages, I've used some 20 or so since I started 20 years ago. I did a fair amount of commercial Prolog development after I left university, I really like Prolog. It makes certain things really easy and it's a joy to code certain types of solutions in, but I'm never going to write a web-app, or a word-processor in Prolog.
Many of these languages are very clever when it comes to doing certain things, but how often do you actually need to do those things?
The truth is that the vast majority of the software out there does pretty dull, mostly procedural jobs. That's why the main languages in use are just dull variations on the procedural, C/Java/Perl style. No matter how much maths geeks go on about functional programming, procedural systems will always be more suited and easier to use for most of the problems out there.
That isn't to say there is no place for these alternative languages, but it's a smaller one which you probably won't see very often.
Paul
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How often do you actually need to generate infinite sequences?
Actually, when you're able to do it naturally in your language, it becomes a very useful thing to do. For example, when you want fresh variables in a compiler, it's very useful to have the infinite list of variable names you haven't used yet hanging about.
How is X better than Y? (Score:4, Informative)
How is that better than doing (or basically the same in Java/C/perl/ruby/etc.):
I hate to say "you're missing the point" because I feel that's unreasonably dismissive - though I kind of feel you are...
IMO the point isn't necessarily that one method is "better" than another - it's that this idea represents an important and useful way of approaching programming problems. If you understand the style you can appropriate it - it becomes a useful concept for expressing problems and their solutions.
So for instance - while you may not use recursion in C for general problem solving (due to the lack of tail-recursion optimizations which turn the thing into a loop) - understanding the recursive expression of a problem is useful for structuring your solutions, understanding what assertions must be made with respect to the state of the data at what points in the code, etc. - even if you structure your solution as a loop rather than a recursion.
And it should be noted that you can implement infinite sequences in C++, etc. - generally the way to do this is with iterators, and the use case would be for feeding those iterators to algorithms that expect iterators... What Haskell brings to the table is that it encourages you to think of problems and solutions in those terms - learn the method and what you can do with it, how it affects the expression of your code - if you find it a useful idea it's easy enough to implement in most object-oriented languages...
Re:Mmmm, Kay. (Score:4, Insightful)
Functors and generators will do the same thing for you in a more mainstream languages like C++ and Python. And they'll be a hell of a lot more understandable to your average still-wet-behind-the-ears programmer. And you can certainly write code in those languages to do lazy evaluation.
Now, I will grant you that, in general, one can do it more concisely in Haskell than one could in C++ and even Python. But these languages are more well rounded, IMO, than Haskell.
Haskell is fun, but painful for procedural code... (Score:2)
Features of Haskell I really enjoy are how it handles constructors, pattern-matched function arguments, user-definable infix operators (with configurable precedence!) and the way it handles higher-order programming and lazy programming. But I never got monads...
Of course, my philosophy is that that's not necessarily a bad thing. Haskell is, IMO, a domain-specific language specialized on functional problems. I feel it's better to have different specialized languages working together well, rather than have
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That is very cool, but does anyone need to do any of those things in the programs that are being created and used today? I'm talking websites, media players, and video games? Haskell may be the coolest thing in the world but maybe not many people need or want the coolest thing in the world. This is always the problem with arguing "but it's better!": things generally only need to be good enough.
If you don't believe me, look at the human race. Do you think that high intelligence or great beauty are driv
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Did you know that FUD does not really mean 'disagrees with what I think'? He never said lazy languages are useless, he mentioned LISP as a language that's still being used. In my opinion lazyness is useful, so let's just wait for an imperative language to steal that feature so people can actually use it, just like what happened with the rest of functional languages' features... (I know people are gonna mod me troll for this, don't worry)
Re:Mmmm, Kay. (Score:5, Insightful)
Haskell only evaluates what it has to -- this program for example which looks up the 3000th element of the sequence will not compute the complexCalculation on the 2999 fibbonaccis before hand like a traditional program would
And then when you actually do use the other values you program is ridiculously slow because the generator function is recalculating the fibonacci number over and over again.
Except you hope that Haskell automatically memoizes the results, but that destroys your smp performance as the CPUs contend over the result cache. So maybe you have separate caches per thread. Then you program grows larger and all the memoization takes too much memory and the system start dropping out results (3000th fib is what 520? bytes). Then you have to go back and tell it to keep the results longer for that function.
In the end maybe you just make it a list that's precomputed.
But that's really beside the point, because you can do the exact same thing in Smalltalk, Ruby, JavaScript, etc, with most of the same costs and benefits. So really the question is, what makes it better than Smalltalk? It's faster at maths, but that's about it. But it has a harder/alien paradigm, the syntax is foreign, etc. Maybe that's why afaik mainly Haskell is only being used by people that crunch numbers ?
Re:Mmmm, Kay. (Score:4, Insightful)
Except you hope that Haskell automatically memoizes the results
Please don't take this the wrong way, but please stop spreading your misinformation. One doesn't hope Haskell memoizes because it doesn't memoize functions. One requires that Haskell implement call-by-need. Overlapping but very different concepts. I'll assume it was an honest mistake but the difference makes the rest of your post nonsense.
Haskell is only being used by people that crunch numbers
Another point of dissagrement. If anything number crunchers (e.g. scientific computing in which I've done a fair bit of work) avoid Haskell (along with anything that is not Fortran, Matlab or C). Haskell finds favor more among "programing language" types who are interesting in writing their own language (Haskell is a phenominal language to wrong another language in) or in "elegant" ways to write compact solutions to traditionally verbose problems (e.g. merge sort in two "statements").
Re:Mmmm, Kay. (Score:4, Insightful)
paraphrase comment #1: Haskell is too academic to be useful.
paraphrase comment #2: No it isn't, here's how to do something with a fibbonacci sequence.
Uh, you failed at "fibbonacci" to make your point. :)
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It's only difficult to read if you don't know it. I personally (being experienced in both Haskell and a wide variety of imperative languages) find it much easier to read than any of the imperative languages I've looked at.
Re:Mmmm, Kay. (Score:5, Insightful)
It's only difficult to read if you don't know it.
That is true of almost any language. The point is that there's nothing those languages can do that can't be done, often more easily, with the current crop of popular languages. Elegance cannot beat convenience in the workplace, or in most at any rate.
All that aside, how many Haskell programing jobs have you seen advertised lately? Like it or not, that's what decides which languages people use.
That's why I have to deal with languages I'd prefer to never use, because that's what pays the rent. In my own time I use C.
Re:Mmmm, Kay. (Score:5, Interesting)
I've seen quite a few Haskell jobs advertised recently actually, I even got one of them :).
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That is true of almost any language. The point is that there's nothing those languages can do that can't be done, often more easily, with the current crop of popular languages. Elegance cannot beat convenience in the workplace, or in most at any rate.
That was the point of the examples he gave there are lots and lots of things that are easier to do in lazy languages than in mainstream languages. Huge blocks of code simply aren't written because they aren't needed.
Re:Mmmm, Kay. (Score:4, Insightful)
No. It's not because of a huge lib. It's because code can be so much more generic than in other languages. And that's the biggest point/plus in Haskell. You don't have to write a new for loop for everything. Even the for loop is abstracted (map, fold, zipWith, ...). And this works with everything. I have yet to find something that's not generalizable in Haskell,
Your 4GL claim turns out to either be true for all languages with a compiler or
the Haskell compiler is just an abstraction you do *once* instead of reinventing it every time and using it in a crude and ugly way, like in C or similar languages,
Your real problem with Haskell is that it is more complex per written token, and so you have to think more per token. Most people seem to generate some inner fear for things they don't understand as good as they expect. And that's the base of all your motivation to find reasons why you dislike Haskell.
Of course you could simplify it, and get something like Python. But this is a bad idea on the long run, because then nature will only create bigger idiots. It's better to wise up a bit, because what you get then, is really really nice!
P.S.: I once tried to design the "perfect language". I stopped as soon as I learned Haskell, because it was not only extremely similar to what I had created myself, but even much better.
quantification of productivity (Score:3, Insightful)
Re:Mmmm, Kay. (Score:5, Funny)
That underlying C code is what needs to be written carefully, because you use Haskell itself to write its own compiler.
There's a Haskell compiler [haskell.org] written in Haskell already. Where does C fit in to that?
After the 'l' and before the 'o'.
Re:Mmmm, Kay. (Score:5, Interesting)
The point is that there's nothing those languages can do that can't be done, often more easily, with the current crop of popular languages.
At University, I studied SML, and came out with a opinion similar to yours concerning functional languages. But when I started to learn Haskell on my own, really learn it, I found that all the concepts in my CompSci courses that seemed so pointlessly complex before, just fell neatly into place.
I'll give you an example of a case where my solution in Haskell to a problem was rather better than any solution I came up with in C#. A while ago I was designing a program to export some hierarchical data held in a database to XML. Because SQL resultsets are 2D grids, I needed a way of converting a 2D grid into a list of fixed-depth tree structures.
In Haskell, the solution is two lines of code, and assuming you know Haskell pretty well, it's fairly clear as well:
I'd be interested to see if you could mirror the functionality in one of the 'popular' languages you mentioned. Perhaps something in Java?
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import java.util.*;
class Node {
Map<String, Node> map = new HashMap<String, Node>();
static Node asNodes(List<List<String>> input) {
Node nodes = new Node();
for(List<String> row : input) {
Node node = nodes;
for(String column : row) {
if(node.map.containsKey(column) == false) {
node.map.put(column
Re:Mmmm, Kay. (Score:5, Insightful)
I'm not going to take the time to look up the appropriate API calls at the moment, but I believe it's somewhere in the range of 2-3 lines of code to accomplish this feat.
If you're not going to take the time to actually produce any code to back up your point, why bother replying?
The biggest problem with talking about the advantages and disadvantages of programming languages is that people tend to make vague claims without producing any evidence for their case. Can JPA produce lazily produce a hierarchical tree of objects from a single database query? I don't know; it's not an answer you're likely to find in an FAQ or a tutorial. And how much work is it to actually set JPA and XStream up? Does it really only take 2-3 lines of code?
Without providing working code, who knows whether your assertion has any merit or not.
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Except nobody can read that. The line noise up there with perl!
Nonsense. You need to be familiar with Haskell's syntax, but once you are, it's as clear as it can be for what it does.
Reading the Haskell in evaluation order:
Filters out blank lists.
Groups rows whose first column is identical.
This uses a function from Control.Applicative, but once you know that:
It's not so scary. It takes the first cell from the first column
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1. Start with a grid of data
2. Filter out empty rows
3. Group rows together that have identical values for the first column.
4. Make a tree branch from each route, using the value of the first column as the head of the branch, and use recursion to find the child branches from the remaining columns (i.e. every column but the first) of the grid.
So:
Becomes:
Re:Mmmm, Kay. (Score:5, Interesting)
Depends on how you determine "easy to read". The main difference between Haskel and say C is that Haskel is very dense while C is not so much, so one line of Haskel holds a lot more information then C, which of course makes look like its Haskel harder to read, since understanding a line of code requires effort, while its trivial in C. However that line of Haskel might contain the same information as a whole function in C and reading that whole function in C might turn out harder then comprehending that single line of Haskel.
All that said, I don't consider the syntax of Haskel very good, lack of parenthesis around function arguments certainly doesn't help readability and the error messages can be rather obscure as well.
A broader perspective (Score:2)
Just because a language is not widely used outside academia does not mean it isn't a good teaching tool. You can pick up a new language in a few weeks, but a strong understanding of the fundamentals lasts forever. In a teaching setting, you want a language and dev tools that do not get in the way of illustrating the concepts.
At my university, a professor chose C++ to teach computational linguistics to non-programmers. HUGE mistake! We spent about 80% of the course learning C++ badly, rather than linguis
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Plus I find they do not scale well for larger application.
And you discovered that through your own experience with functional programming languages, did you? It's remarkable that you could have gained such insight, yet not know how to spell the name of one of the best-known FPLs in town.
I rather suspect that, like many critics of FPLs, you have never actually tried to use them for a big project, and just assume that they won't scale because you read it somewhere.
But today most developopment is for larger application which doesn't necessarly solve problems per-say but create a tool that people can use.
I'll gloss over whether your unverified assertion about "most development" is actually true. Even assum
Too constrained and academic (Score:5, Insightful)
A separate, but related problem is that the community doesn't seem interested in practical use of it - there aren't lots of bindings to libraries to make easy things easy. Heck, even doing i/o at all isn't really supported very well. Functional programming is very good for the pure computer science part of programming, but unfortunately that's going to make up less than half of any given program. You also need to be able to interface.
So I think the quote in the summary is right: people won't be adopting Haskell or similar pure-functional languages any time soon. What will happen is the next generation of dynamic languages will adopt the best features from functional programming; we've seen that happen already in python and ruby, and it'll happen again. And people will start using them there.
Re:Too constrained and academic (Score:5, Interesting)
A separate, but related problem is that the community doesn't seem interested in practical use of it
Really? That's why there's a new book called Real World Haskell [realworldhaskell.org]. The IRC channel on freenode is one of the largest on the entire network, and full of people doing real world things with haskell.
there aren't lots of bindings to libraries to make easy things easy.
I call FUD. The Hackage database [haskell.org]has literally hundreds of libraries sat there ready for you to use. And if you really need something that isn't there, the FFI is mature, and very easy to use.
Re:Too constrained and academic (Score:4, Insightful)
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I think the real problem with Haskell is that you're required to use your brain to make any use of it.
What, you mean you can't just bash your head against a keyboard repeatedly and expect your program to compile (but not necessarily work? Call me irrational, but hey, I see that as a good thing! Making programmers think before they write something, and then having it work first time is great!
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And even if I give you that, it's still an order of magnitude fewer than you'd get with more popular languages.
Really? Ruby forge has a fairly similar number of projects available. PyPi has only a small amount more. Last time I checked with the guys who manage hackage, they're getting 100 submissions of new projects/versions every *day*.
Please. No such automatic interface is reliable enough to depend on - they always break on the one function you particularly need. The FFI is not a real solution.
Automati
visibility of hackage (Score:4, Insightful)
Hackage is well known to haskell programmers. It is linked to directly from the front page of haskell.org, it is mentioned frequently on the haskell-cafe mailing list, and that's where hundreds of haskell projects [haskell.org] are hosted. If you're an average passer-by and not an active haskell developer, it's not necessarily going to jump out and say "boo!", but it isn't hiding under a rock, either.
Note: hackage is not the standard libraries. Those are documented elsewhere [haskell.org].
Re:Too constrained and academic (Score:5, Interesting)
You also need to be able to interface.
Which is exactly why I find Scala [scala-lang.org] to be interesting. Note: I haven't had time to learn or use it yet, but the design concept there is very interesting.
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I've been using Scala and it's the only way to do anything with Java, imho. Sure, it's no Haskell but it's pretty darn nice. A lot nicer than Java without the performance penalty of other languages that target the JVM, such as Groovy or Python.
Even if you don't have to use Java, the popularity of the language combined with the pervasive NIH syndrome of the community means there is a very rich library of software components to use.
Re:Too constrained and academic (Score:5, Interesting)
Very true, I did a large project in Haskell for a CS class once the three of us working on it hated the language after we were done.
Before that we were pretty happy with Haskell, because the programming assignments leading up to the final project were all fitted to the language, but the instant we had to do something that wasn't, we realized what a mess it is.
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Right in the middle of reading your comment I realized they must have changed something in the Matrix again.
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This is only true for specific implementations. The Haskell 98 report only specifies library support for textual input/output, and is completely useless for portably handling Binary IO. That everyone just uses GHC anyway, which has great support for Binary IO, doesn't negate the point that Haskell itself sucks when it comes to IO.
Other serious shortcomings would have to include lack of proper locale/encoding support (characters are read in as Unicode values; but what is the original encoding assumed to be,
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Correct-a-mundo. On the Haskell part at least. Javascript is a functional language that has managed to go mainstream. Whether you would call it "pure" or not is open for debate.
Re:Too constrained and academic (Score:5, Interesting)
No, I mean it is a true, honest to God, functional language. If you check Wikipedia, for example, you will see it listed as "Multi-paradigm: prototype-based, functional, imperative, scripting".
See, most people look at the C-style syntax and think it means that Javascript is a C-style language. Then they get frustrated when the C-stlye code they write looks like crap. Instead, they should be coding with closures and lambda, much like they would with a LISP program. The result is a far more sophisticated program that performs more work with greater elegance than a C-style equivalent.
I highly recommend Douglas Crockford's "The JavaScript Programming Language" [yahoo.com] introduction to the language if you're not familiar with Javascript's functional aspect.
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That a language has "functional aspects" doesn't make the language itself "functional". By the same reasoning you use, Python is a "functional language" too. Hell, even Perl has closures and lambda. And Python has list comprehensions and such. Pretty much every high-level language has these things; that doesn't make them functional.
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What would you describe as "Functional" then? i.e. What is the key difference between a Functional language and a language that has "Functional Aspects"? Show me the difference you believe is there and I'll show you the Javascript goods.
Oh, and BTW? Academia agrees with me that Javascript is a functional language.
Re:Too constrained and academic (Score:5, Interesting)
So, if you can show me that you can't have mutable variables in Javascript, we can call it functional.
Re:Too constrained and academic (Score:4, Interesting)
An excellent post, sir. Much more on target than cylence's attempts.
This is correct. However, I did not claim that Javascript is a *pure* functional language, only that it is a functional language. If we go by the definition of a pure functional language, then we must discount a long list of functional languages as well. That includes the poster-child for functional programming: LISP
Javascript allows for pure functional programming just like any other functional language. However, it does not enforce the purity of functional code. Something that is a very difficult goal to reach. This combined with the C-Style of the language has the negative effect of encouraging imperative programming. With suitably predictable results. (How many times have we heard, "Javascript sucks!")
This is why I often refer to Javascript as a "LISP-style functional language". The two don't line up exactly, but the foundations of Functional List Processing are present in both.
An interesting aspect of the language's real-world use is that the designers of Javascript's web APIs could have created APIs that force imperative thinking. Yet they didn't. Even for traditionally imperative operations (e.g. networking), the designers of Javascript's web APIs have seen fit to ensure its functional nature through the use of an event system. e.g. I do not read values from XMLHttpRequest, I wait for a functional call.
I personally think it's fascinating that the functional underpinnings of the language have been so well preserved despite the lack of general knowledge about the language. The efforts they are putting into the language will pave the way for more mainstream functional languages in the future.
Re:Too constrained and academic (Score:4, Informative)
There's a more in-depth article on Javascript's functional capabilities here:
http://www.hunlock.com/blogs/Functional_Javascript [hunlock.com]
Other stuff I pulled out of Google for your perusing:
http://dankogai.typepad.com/blog/2006/03/lambda_calculus.html [typepad.com]
http://math.ucr.edu/~mike/lc2js.html [ucr.edu]
http://www.joelonsoftware.com/items/2006/08/01.html [joelonsoftware.com]
http://www.ibm.com/developerworks/java/library/wa-javascript.html [ibm.com]
What this all means is that Javascript is the most widely deployed functional language in existence! And that's a fact you can take to the bank.
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Has a lot of lazy evaluation stuff in libraries.
Has modifiable syntax/grammar.
Very efficient - number 2 after "C".
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Them there what ?
Why they don't rule: (Score:5, Funny)
Re:Why they don't rule: (Score:5, Informative)
The picture in the linked article is missing a beard.
I was going to mod you funny, then I thought maybe a lot of people wouldn't get the beard reference [microsoft.co.il], so I decided to post instead. Anyone else want to mod parent funny?
Re: (Score:2, Funny)
Re:Why they don't rule: (Score:5, Funny)
Anyone else want to mod parent funny?
Yes, I will!
Oh crap.
It's not for dumb people (Score:5, Insightful)
I haven't really been able to figure out how to do anything significant in Haskell. But I suspect that one day a language more like haskell and less like C will end up being the most popular. Monads and all that kind of confuses me.
I think it helps if you have a strong math background and are comfortable with Lambda calculus. I'm just an old C hacker and haven't used any real math in like 10 years, so I'm not that effective in Haskell :(
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Personally I'm pretty happpy with pthreads and C anyway... I've yet to be sold on any of these new languages.
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I can get things done in C, and it pays the bills. So I'm not complaining. But I think that letting the compiler figure out the threading for you will be the way of the future when something as simple as a cellphone consists of 300+ minimalistic processing cores working together.
It seems unnecessary today to thread out for more than a dozen cores, but maybe some future technology will require a fair amount of processing power to operate. Perhaps holographic projection need it to encode/decode a data stream
Re:It's not for dumb people (Score:5, Funny)
Don't worry.
In a few years you will see c++++ which will be c++ with functional programing tacked on. Of course you will also see Functional Object C but only Apple will use that.
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Well, that C++0x thing or however its called has lambdas and functions closer to being a first class construct...so thats pretty much exactly whats happening already, give or take :)
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I should have learned this a long time ago.
Don't try and make stuff up to be funny. The truth is silly enough without my help.
All I can say is ewwwww..
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C++'s template system is actually a Turing-complete functional programming language.
-Chris
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Monads and all that kind of confuses me.
And that's exactly the problem. What are Monads? I'm not really sure (I sort of have a vague intuition of what they are, but that's it). But I do know that you need them in order to do anything that involves side-effects in the world outside of Haskell. And that includes I/O. Yes, that's right, you need to understand a rigorous mathematical construct in order to write a "Hello World" program. There's simply *no way in hell* a language like that will become popul
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That's like saying you don't *have* to understand how I/O works to write data out to a file. Yeah, it's true, but any developer worth his title must.
Besides, basic I/O is just one case of side-effects, and Monads are ridiculously hard to understand and work with relative to procedural solutions to the same problems.
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Welcome Perl. Read Higher-Order Perl ( http://hop.perl.plover.com/ [plover.com] ) if you don't believe me.
Best of all, it's always installed on all unix boxes (including macs!)
The only thing that's lacking is automatic palatalization across many cores for map{} operations, but I'm sure I can write a custom iterator to bucket things into N-threads on N-core CPUs if such a need arises.
Arrrr, it's Stephenson again! (Score:3, Funny)
I haven't really been able to figure out how to do anything significant in Haskell. But I suspect that one day a language more like haskell and less like C will end up being the most popular. Monads and all that kind of confuses me.I think it helps if you have a strong math background and are comfortable with Lambda calculus.
Monads, lambda, calculs...arrr, matey, now I know why Haskell's such a bloody mess - Neal Stephenson wrote it! That be why it seems good at first and falls apart at the end.
Re:It's not for dumb people (Score:4, Interesting)
People will get more intelligent just by using functional languages.
Don't be ridiculous. Functional vs procedural isn't a matter of intelligence. It's simply a way of thinking. And the reality is that procedural languages better match the way the human mind works.
IMHO, learning to program in a functional style is like a right-handed person learning to write with their left. Yeah, they can do it, but it requires a ton of work for dubious real-world benefit, and in the end, it's never really natural, simply because that's not the way the brain is wired (except for the odd freakish exception ;).
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And the reality is that procedural languages better match the way the human mind works.
To quote you -- don't be ridiculous. From my personal experience of teaching people functional programming, it's nothing to do with imperative programming matching the brain better. Instead, it's to do with people learning to write imperative programs first, and then having a very steep unlearning curve to deal with at the same time as the learning curve for functional programming.
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I don't think there is any evidence that procedural languages are easier to understand; SQL, which (like functional languages) is declarative rather than procedural seems to be at least as simple as most programming languages for even neophytes to understand.
Procedural programming is probably easier to understand if you started out for years learning procedural languages, or if you come from a hardware-centric background;
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There, fixed for you.
There's nothing natural in the "change-one-byte-at-a-time" von-Neumann bottleneck [stanford.edu] languages, other than they're the ones taught in standard programming courses.
Oh, you mean that the human mind keeps track for changes of state in the environment? Sorry to break the news to you, but that can also be done in functional languages. [wikipedia.org]
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As for an "instance of a normal, everyday situation in which humans use a functional model of computation":
SELECT Name, Age FROM My_country
WHERE Age > 18
GROUP BY Age
You'd be hard pressed to find someone thinking of the age groups in their country using a "for..next" model.
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Schools teach functional languages to this purpose. There is no evidence that this is true, but it fills a couple hours of lecture time every semester.
Rule? (Score:2)
one of the best practices (Score:3, Interesting)
We can see this philosophy in C where, except where huge data structures are involved, it is best to make a copy of data rather than work to work on someone else's copy. Likewise functions do one thing, do it well, and, again except for huge data structures, return a copy. Memory is manually allocated, and deallocated, possibly from the functions local heap.
It is interesting to me how it all comes back to just best practices. Make sure you know how much memory you need. Make sure you are only doing what needs to be done right now. Make sure the interfaces are clear. If data is ready, then it should be ok to work on it. To me functional programming is what happens after data models, or objects, are defined. Once the data structure is defined, you can treat it as stateless immutable input. Output is a another structure. Again, the only limitation is if the object is so large that duplicating become a cost performance issue.
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We need a simple language - C
This OO thing is nice - C++
This Virtual machine thing is nice - C#
Lazy Functional languages are nice - C@ ?
If in doubt bolt it onto C ... ;-)
Interview (Score:2)
It figures that this article would be an interview. That way Simon Peyton-Jones didn't need to evaluate the answer to any question until it was asked.
Lazy Functional vs Lisp? (Score:3)
What's the difference between a functional language like Lisp and a lazy functional language?
Just asking.
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Lazy evaluation means that a value won't be calculated until it is absolutely necessary. So in the example in the above discussion, you can make things like an array of all the Fibonacci numbers. This works because the environment won't actually calculate anything until it is necessary.
Lisp doesn't support this behavior by default. In LISP all function arguments are evaluated left to right. Although using macros, you could probably write your own lazy evaluation mechanism.
The lazy language (Score:3, Funny)
Re:Lazy Functional vs Lisp? (Score:4, Interesting)
In a lazy language (more properly called "call-by-need"), every expression has a thunk wrapped around it and thunks are automatically forced. (They have thunks in Lisp/Scheme but they must be explicit rather than implicit.)
Lazy languages allow you to "use" values that haven't been defined yet. For example
a = 1 : b
b = 2 : a
Which would produce two lists of alternating ones and twos (a starts with 1 and b starts with 2; also ":" is infix "cons").
In Scheme (which I know better than Lisp), you could accomplish the same with
(let ( [a (cons 1 #f)]
...)
[b (cons 2 #f)])
(set-cdr! a b)
(set-cdr! b a)
But being lazy (1) frees you from thinking about order of evaluation and (2) allows some constructs to be expressed more easily (e.g. taking the fixed point of a composition of functions (example to complicated to post here)).
At the end of the day, any program written in one style can be written in the other so its all differences of ease and different ways of thinking about the program.
Oh my god! (Score:4, Funny)
Combinatorial Parsers, etc. (Score:3, Interesting)
One thing in Haskell that always intrigued me was the idea of combinatorial parsers - a parser that accepts a string and yields not a single parse tree, but all possible parse trees based on the language rules... Simple implementations of those can be implemented in Haskell pretty straightforwardly. Combinatorial parsers for individual rules are stuck together - and while rules may generate a bunch of possible parse trees these are culled by successive rules...
I don't know too much about the practical efficiency of these - but in terms of how they're expressed I think they're great...
Transactional Memory (Score:3, Informative)
Thoughts on Haskell, from a Haskell programmer.
Haskell has a very nice software transactional memory [haskell.org] library, which makes a lot of otherwise-difficult concurrency problems much easier. It's statically safe, too, unlike similar libraries for imperative/OO languages.
Certain other language features are very nice. Monads are also extremely powerful once you wrap your head around them, and the type-class system and standard libraries make a lot of math programming problems much easier.
The language also has downsides. The laziness makes it possible to build up an arbitrarily long chain of suspended computations, which amounts to a hidden memory leak. Laziness also complicates the semantics for "unchecked" exceptions, most notably division by zero. The combination of laziness and purity can make the language very difficult to debug and optimize. While the compiler has very powerful optimization capabilities, sometimes code needs to be just so to use them (like flagging things "const" or "restrict" in C), and this can make it hard to write clean code that runs fast.
The other problem is that most programs need some amount of imperative code somewhere to do the I/O. This code has a tendency to be verbose, nasty and slow in Haskell.
There are also some problems that would be relatively easy to solve in a very nice way within the semantics of the language (give or take), but are not solved well in the standard libraries. These include exception handling, global mutable state, strings and regular expressions, certain I/O operations, arrays and references. It would be very nice if the ST and IO monads were unified, and if references and arrays had nice syntax; this would reduce the ugliness needed to write those occasional bits of imperative code.
Re:Why "lazy"? (Score:5, Informative)
They're "lazy" because they don't do any work until necessary. For example, a function can return an infinitely long list, but only the elements you request will actually be calculated. Or, to compare them to Python, it's like having everything function like an iterator.
Re: (Score:3, Insightful)
Well Haskell isn't "smart" in the sense that it goes out and arbitrarily caches things it thinks may be helpful (that way leads to madness).
It does cache computations it's made if you store them in a variable or part of a data structure, so if you plan things right, you can get the behaviour you want.
Basically, here'
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so I'm not the only one thinking along those lines - good to know.