Dear Phiroc, I am also a newbie to Haskell, but I also must confess having a sort of religious conversion. I also admit that the learning curve for Haskell, and in particular associated theory is steep, and I am only on the fist rung of the ladder. Some of what I say here has been echoed by others in answer to your query on the utility of Haskell. I think most would agree that a language, be it natural or artificial, constrains or enhances they way you think, and perhaps even what you can think, and what you can create. Historically many technical problems remained intractable until the invention of the right language, the language of classical algebra, or the differential calculus I think are good common examples. Who would argue that Italian is a great language for operas? I find even at the elementary level, many common algorithms seem to me naturally obvious when expressed in Haskell. Other have also pointed out that the category theory constructs that allow Haskell to remain a purely functional language, allow you to bring in 'the heavy guns' of standard mathematical reasoning. With out discussing what proof is really all about, it very powerful if that concept can be imported into the art of programming. I also think that the relationship between parallel computing and functional languages will become very important in to following decades as we hit 'Moore's wall'. Now for my real truth, it is just down right great fun, hacking at its best. If asked for a one line description on what Haskell is I would say that it is 'Lisp on steroids'. Paul Graham has plenty to say about the utility and elegance of Lisp, I would like to know what he thinks of Haskell. I am going to paraphrase Graham: 'If a lot of really smart people are using something, and you can't see why, maybe its worth your time to see if you can see what they see'. Just to give you an idea of where I am coming from I started out putting food on the table in the 70's writing PDP 11 assembler programmes. Suppose you don't even use Haskell in a project directly, maybe you develop your programme 'conceptually' in Haskell, and write it in whatever makes practical sense in your environment and market. You may end up with an artfully designed set of code, that is easier to maintain, with clear abstraction barriers. In assaulting the learning curve I have found that I am building up a collection of texts, papers, blog postings, etc. If I don't understand one source, maybe another will give me some insight. I will just mention one of the many reference that I have found useful: 'Functional Programming - Practice and Theory' By Bruce J. MacLennan (ISBN 0-201-13744-5). Oh, and of course the classic, 'Structure and Interpretation of Computer Programs' by Ableson and Sussman. Neither is an 'Hakell' book, but I have found them hyper-useful for practical foundational material. I would be interested to know what materials you are using to learn Haskell, and am glad to see that I am not the only 'newbie' :-) Best Regards, Robert Emerson P.S. I didn't even mention Domain Specific Embedded Languages! Big time advantage. On Friday 27 April 2007 01:02, phiroc@free.fr wrote:

If this is interesting then please enlighten a poor, ignorant PERL hacker.

Quoting Johannes Waldmann :

...

phiroc@free.fr wrote:

...

[...] semi-functional programming languages such as Perl [...]

now this is an interesting view ...

_______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell

On 4/26/07 10:13 AM, Joe Thornber wrote:

On 26/04/07, Johannes Waldmann wrote:

...

phiroc@free.fr wrote:

...

[...] semi-functional programming languages such as Perl [...]

now this is an interesting view ...

I seem to remember someone writing a book on functional programming in Perl, which seemed odd to me.

For the record, you're probably thinking of Higher-Order Perl, by Mark Jason Dominus. HTH, Keith http://www.amazon.com/Higher-Order-Perl-Transforming-Programs/dp/1558607013

Java sense (i.e. "cut out any feature that can't be understood in five minutes by a chimp") Got to love comments like this they are constructive, objective, mature and accurate. Glad we have your expert opinion to give us the gospel. Can I get an amen? How about a Hallelujah ? Troy Taillefer Java chimpanzee ________________________________ From: haskell-bounces@haskell.org [mailto:haskell-bounces@haskell.org] On Behalf Of Sebastian Sylvan Sent: Thursday, April 26, 2007 1:27 PM To: phiroc@free.fr Cc: haskell@haskell.org Subject: Re: [Haskell] Newbie: what are the advantages of Haskell? (note to Haskellers: Yeah, I'm handwaving things here, no need to point out counter-examples to my generalisations!) On 4/26/07, phiroc@free.fr wrote: We'll do this one first: What are the mysterious "side effects" which are avoided by using Haskell, which everyone talks about? Null pointers? Side effects are usually things like mutable state. In Haskell variables don't vary. "x=x+1" isn't valid in Haskell. This means, among other things, that functions always do the same thing given the same input (they can't depend on some mutable state changing value), which is great since you'll never get those "oh I forgot that I must first call foo before I call bar, or I'll get an error". This really is a HUGE win, since programming with state is unreasonably error-prone. I'm afraid it's next to impossible to convince anyone that this is true, unless they're willing to give it a serious try, though :-) Null pointers are possible when you're dealing with C functions mostly. You don't use pointers in Haskell normally, only when you're interfacing with external C libraries etc. Hello, what are the advantages of haskell over semi-functional programming languages such as Perl, Common Lisp, etc.? For me? Purity. I mean you can get plenty of the benefits of FP in any old language (witness C# 3.0), but the one thing you can never get by just adding support for a "functional style" in another language is purity. Once purity is gone, it's gone! It can't be retrofitted on an existing language. Purity is great because it makes it much easier to write programs without making silly mistakes. When writing programs in languages with lots of side effects you have to sort of keep a "mental log" in your head for all possible execution paths ("in this branch x is equal to y plus w, and this pointer here is null in the other branch x is null and..."). For me I can quite literally *feel* "brain resources" being freed up when using Haskell, which I can use to get stuff done quicker (or probably more accurate: I can feel how much brainpower I waste on book keeping and keeping track of this "mental log" when using languages like C++). Also purity is very interesting when you want to paralellize programs (a pure function can be executed on any thread, at any time, and its guaranteed to never interfer with the computation of other functions -- in impure languages this doesn't hold at all!). This is probably the killer app for functional programming IMO. FP is cool for a number of reasons, but I think "isn't almost unusable in a multithreaded setting" is what sets it apart the most from imperative languages. Haskell also has STM which is great for that low level shared state concurrency that you sometimes need (no locks, monitors, or any of that non-composable, insanity-inducing, messiness!) Aren't Haskell's advantages outweighed by its complexity (Monads, etc.) and rigidity? I can sometimes feel that Haskell looses out on not being user friendly in the Java sense (i.e. "cut out any feature that can't be understood in five minutes by a chimp"). Some things do take some effort to learn, but there is a huge payoff for it (it's really powerful!). But yeah, there might be plenty of folks who will never bother learning about them, and they won't understand your code. -- Sebastian Sylvan +44(0)7857-300802 UIN: 44640862

Am Freitag, 27. April 2007 18:18 schrieb Al Falloon:

[…]

IOW: Java's advanced features are separable from its basic features. I.e. you can teach Java without teaching generics or anonymous inner classes. In Haskell, OTOH, you can't even learn how to do IO without learning Monads, or at least glossing over oddities like a new syntax. And thats not even getting into issues like statelessness and lazy evaluation.

As for Java, this is not quite true. In Java, you cannot write a “Hello world!” program without stumbling over classes and static methods. And if you start using I/O, you will soon have to deal with rather complex class and object structures. (At least this used to be the case.)

[…]

Best wishes, Wolfgang

Admittedly, this is phrased in an inflammatory manner, however, the original sentiment >>is actually pointing out an advantage of Java over Haskell. Here is the original >>>.paragraph in context:

This not the first inflammatory comment he has made

...

But, Sebastian is right. Sebastian will be right when I see Chimpanzees coding in Java :)

...

The leap is worth it. I am not so sure it was for me. I guess It depends on what you are looking for I have spent the last year learning Haskell and I have learned some very interesting concepts. I can't help but wish that Haskell turned out to be a more practical language for me to code something useful in every time I looked for Haskell libraries I was a disappointed. I can't help feeling that last year might have been better spent learning Erlang (which is this years language for me to learn).

I really enjoy Functional programming (at least until I try to do something serious then frustration sets in). I can't produce software in a timely and cost effective fashion without a large body of high quality, documented and maintained libraries. I get the feeling that Haskell is for researchers to explore ideas about programming in but no one is interested in doing The grind work of cranking out useful basic libraries. I guess you need borrow some of those Java Chimps :). Am I the only person on the list that feels this way ? I guess I am feeling a bit bitter of spending so much time on Haskell and having so little to show for it. Troy -----Original Message----- From: haskell-bounces@haskell.org [mailto:haskell-bounces@haskell.org] On Behalf Of Al Falloon Sent: Friday, April 27, 2007 12:19 PM To: haskell@haskell.org Cc: haskell@haskell.org Subject: [Haskell] Re: Newbie: what are the advantages of Haskell? Taillefer, Troy (EXP) wrote:

Java sense (i.e. "cut out any feature that can't be understood in five

minutes by a chimp")

Got to love comments like this they are constructive, objective, mature and accurate.

Glad we have your expert opinion to give us the gospel.

Can I get an amen? How about a Hallelujah ?

Admittedly, this is phrased in an inflammatory manner, however, the original sentiment is actually pointing out an advantage of Java over Haskell. Here is the original paragraph in context: Sebastian Sylvan wrote:

I can sometimes feel that Haskell looses out on not being user friendly in the Java sense (i.e. "cut out any feature that can't be understood in five minutes by a chimp"). Some things do take some effort to learn, but there is a huge payoff for it (it's really powerful!). But yeah, there might be plenty of folks who will never bother learning about them, and they won't understand your code.

IOW: Java's advanced features are separable from its basic features. I.e. you can teach Java without teaching generics or anonymous inner classes. In Haskell, OTOH, you can't even learn how to do IO without learning Monads, or at least glossing over oddities like a new syntax. And thats not even getting into issues like statelessness and lazy evaluation. So for a new user, Java is the better language. You can get into its features slowly and as you see the need for them. Haskell requires you to learn a number of mind-bending concepts right up front. Java has a gentle learning curve and Haskell has a vertical jump. But, Sebastian is right. The leap is worth it. Its the same as what someone once said about LISP: even if you never get to use Haskell regularly, you will be a better programmer when you finally "get it". _______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell

mike clemow wrote:

Troy,

As a Java chimp embarking on the Haskell journey myself, I'd be interested in hearing about specific ways that learning Haskell has changed the way you program Java. How do you employ the "very interesting concepts" that you have learned through your study of Haskell in your Java programming? Do you employ them at all? _Can_ they be employed in Java? Has it made you a better Java programmer?

Cheers, Mike

I reinvented functional programming when I was using Java rather than Haskell making me use Java more succintly. I knew something was seriously wrong with imperative programming and Java's type system all those years I spent working on the implementation for IBM. I was pleased to learn that Haskell incorporated many of my ideas (and more) - validating my original suspicions. The fact that many of the concepts in Haskell I had already "invented" made the language easy for me to learn (as in, "oh yeah of course that makes perfect sense" in response to discover monads). I produced many Java projects in an attempt to demonstrate what I thought was wrong, but few of them remain due to loss of interest. http://jtiger.org/ http://code.google.com/p/pure-functional-java/ In regard to the original question, 'What are the mysterious "side effects" which are avoided by using Haskell, which everyone talks about? Null pointers?', my response is "yes". Looking at a NullPointerException (NPE), these exist because of the imperative nature of the code; with explicit order of evaluation and potential side-effects. In an attempt to highlight the absurdity of the fact that a NPE even exists, I like to tell people that "NPEs occur when you write a program that says, 'give me the something that is not there yet'". Now, if you have read Stephen Hawking's Brief History of Time and the chapter titled, Arrow of Time, you will know that "the arrow of time will not reverse". How absurd it is to suggest otherwise by imperative programmers! Simply, a programming language that allows an expression of "give me the non-existent something" contains a logical absurdity. let p(something) = something exists let q(something) = something is non-existent let r = p ? ¬q let s = p ? q therefore r therefore s but r ? ¬s !! I have long considered (well before I knew about Haskell) formulating a more concrete proof that imperative programming contains many logical absurdities. Remember, forall software. software is based on the lambda calculus. I believe that you can prove this. Tony Morris http://tmorris.net/

Derek Elkins wrote:

And then you come to Haskell and you -can- say, "Give me the something that is not there yet."

Please give me the libraries that are not there yet! *duck*

On Fri, 2007-27-04 at 15:37 -0400, Taillefer, Troy (EXP) wrote:

I really enjoy Functional programming (at least until I try to do something serious then frustration sets in). I can't produce software in a timely and cost effective fashion without a large body of high quality, documented and maintained libraries.

I get the feeling that Haskell is for researchers to explore ideas about programming in but no one is interested in doing The grind work of cranking out useful basic libraries. I guess you need borrow some of those Java Chimps :).

Am I the only person on the list that feels this way ?

No. You're not. I wish I knew the language better so I could start working on those libraries. I love the language, but can't use it. -- Michael T. Richter (GoogleTalk: ttmrichter@gmail.com) Never, ever, ever let systems-level engineers do human interaction design unless they have displayed a proven secondary talent in that area. Their opinion of what represents good human-computer interaction tends to be a bit off-track. (Bruce Tognazzini)

Michael T. Richter wrote:

I wish I knew the language better so I could start working on those libraries.

Which ones? "those libraries" cannot come into existence until someone says what's actually missing. (The bulk of CPAN is crap and is certainly not worth being reimplemented.) -Udo -- "Object-oriented programming is an exceptionally bad idea which could only have originated in California." -- E. W. Dijkstra

Hi

HTTP. We also need better availability of libraries, and a more standard and reliable way to install them and specify their dependencies. We could also do with a good debugger. These are being addressed by the Google Summer of Code project.

Hi Neil, a good debugger ? What is in Google Summer of Code about it ? I just found it: http://hackage.haskell.org/trac/summer-of-code/ticket/6 that havent student related. I was studing about debuging techs for haskell to build a nice debugging enviorment in HIDE or some other IDE. It's my bacharelor final work. I and my teacher are thoughting about trying "observes" in a transparent way. The user click and point to in a source local... but the observes dont appear in the code. We will try integrate another technique from HAT in this imaginary (still)debugging interface. If you or some other has suggestions to me, please. Rafael

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Al Falloon wrote:

Taillefer, Troy (EXP) wrote:

...

Java sense (i.e. "cut out any feature that can't be understood in five minutes by a chimp")

Got to love comments like this they are constructive, objective, mature and accurate.

Glad we have your expert opinion to give us the gospel.

Can I get an amen? How about a Hallelujah ?

Admittedly, this is phrased in an inflammatory manner, however, the original sentiment is actually pointing out an advantage of Java over Haskell. Here is the original paragraph in context:

Sebastian Sylvan wrote:

...

I can sometimes feel that Haskell looses out on not being user friendly in the Java sense (i.e. "cut out any feature that can't be understood in five minutes by a chimp"). Some things do take some effort to learn, but there is a huge payoff for it (it's really powerful!). But yeah, there might be plenty of folks who will never bother learning about them, and they won't understand your code.

IOW: Java's advanced features are separable from its basic features. I.e. you can teach Java without teaching generics or anonymous inner classes. In Haskell, OTOH, you can't even learn how to do IO without learning Monads, or at least glossing over oddities like a new syntax. And thats not even getting into issues like statelessness and lazy evaluation.

however, you cannot even print a message without learning a few things about classes. C++ is even worse in this aspect though, using both classes and operator overloading for a hello world. I think the haskell first learning step is quite acceptable if you manage to get the syntax right (beginners tend to mess up indentation rules for do etc)

So for a new user, Java is the better language. You can get into its features slowly and as you see the need for them. Haskell requires you to learn a number of mind-bending concepts right up front. Java has a gentle learning curve and Haskell has a vertical jump.

But, Sebastian is right. The leap is worth it. Its the same as what someone once said about LISP: even if you never get to use Haskell regularly, you will be a better programmer when you finally "get it".

_______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell

- -- - -- - ------------------------------------------------ Johan Henriksson aka Mahogny aka Stålis mahogny@areta.org / johen@student.chalmers.se / johan.henriksson@biosci.ki.se MSc Engineering PhD student, Karolinska Institutet http://www.areta.org http://www.mtek.chalmers.se/~johen/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGMnr9TMgAX9vPlc4RAhqNAJ9lKF+nlEvLJ/vWcQcOSitV1ffnLwCfYl5T tpNKzvDIN+S7XW3ifAl5Ik8= =UvYY -----END PGP SIGNATURE-----