Re: [Haskell-cafe] NumberTheory library
G'day all. Quoting John Meacham <[EMAIL PROTECTED]>: > Ack. I use the MTL quite extensivly in most of my projects. I hope it > won't disapear from the standard libraries completely. For the record, I have no information that the MTL will disappear any time soon. However, the proposed roadmap is to move stuff out of hslibs and into cabal, and that may be the eventual fate of the MTL, especially if someone proposes something better for future standardisation. My real point in all this is that using a state monad for the purpose proposed in the number theory library is (IMO) overkill, despite making the code slightly prettier, and introduces dependencies which don't need to be there. My real real point is that the rules for libraries are slightly different than the rules for programs. Cheers, Andrew Bromage ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] NumberTheory library
On Wed, May 11, 2005 at 01:57:58PM -0500, Brian Smith wrote: > On 5/10/05, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > The MTL might be deprecated soon, > > replaced by Iavor's library, for example. > Is this just a rumor, or is this really the plan? Where is the best place to > get lavor's library? Ack. I use the MTL quite extensivly in most of my projects. I hope it won't disapear from the standard libraries completely. John -- John Meacham - ârepetae.netâjohnâ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Python?
On 2005-05-11, Michael Vanier <[EMAIL PROTECTED]> wrote: > Here at Caltech we teach Scheme first (for programming concepts), then > students can go in several different directions. I remember the changeover from C first, and I think it was a mistake... -- Aaron Denney -><- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
> Date: Wed, 11 May 2005 13:06:51 +0200 > From: Jerzy Karczmarczuk <[EMAIL PROTECTED]> > > Michael Vanier comments my defense of Matlab: > > >>I used objects, and even a lot of functional > >>constructs. I don't see any reason to call it a creeping horror. > >>It is quite homogeneous and simple, and is decently interfaced. > >> > >> > >> > > > >It's incredibly inconsistent. To cite just one example, the syntax is > >geared towards the notion that "everything is a two-dimensional matrices of > >double-precision floating point numbers". If you want to have a > >three-dimensional array, you can do that, but the syntax is not going to be > >nearly as elegant, because matlab's array syntax doesn't scale at all. > > > Come on... > Matlab has cells and the full object-oriented layer nowadays. There > are short ints, strings, complex numbers, etc. The extensibility is > good. The overall consistency is reasonable. > > Syntax for 3D arrays? > Give me one single language where this is natural and immediate. > We are 2D readers/writers, our way of presenting information is > 2D within a text editor, and similar problems hit everywhere. I used > 3D matrices for the image synthesis, for colour image processing, > for simulations of physical systems. It wasn't worse, and even better > than in many other languages. Python: # 2-d array: print a[0][0] # 3-d array: print a[0][0][0] This also applies to most languages, including C. If you like matlab, go right ahead and use it. The same goes for Visual Basic. I could care less what programming languages you use. But if you think matlab is an elegant language, we will have to agree to disagree. And that is the last word I will say on this subject, since this is a Haskell mailing list. Mike ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] subRegex bug?
Am I misunderstanding the regex docs? *MyMod> subRegex (mkRegex "\\." ) "foo.bar" "blah" "foo*** Exception: Text.Regex.Posix.regcomp: error in pattern -Alex- __ S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
Daniel Carrera wrote: This might be a strange question to ask on a Haskell list, but I do want to hear your opinions. What do you think of Python? I learnt it some years ago to do some simple text processing. Eventually I used it for three small projects. I learnt to hate dynamic typing, I learnt to hate that a forgotten 'return' is interpreted as 'return None', I didn't like that some types were mutable and others not. The documentation is poor due to missing types. Maybe it is due to the documentation (indexing) or because of the module structure, but it is hard to find the functions you need. I found that regular expressions are not of that big help for parsing texts. I missed some support for processing data 'on the fly'. Haskell's laziness makes a great job in this respect. I'm now porting one of my Python projects to Haskell and it is really more fun. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monad library (was: NumberTheory library)
Hi, At some point this was the plan, but I am not sure what happened. I haven't heard of any such plans at the moment, although if you are interested in the library (which is in many ways quite simillar to MTL) you can find it at: http://www.cse.ogi.edu/~diatchki/monadLib I have been using it for a while, so at least the basics work. I have done a little profiling, but probably not enough. I don't consider it to be stable in the sense that I am prepared to change it beyond fixing bugs. This may change if more people started using it, but as far as I know I am currently the only user, which also has benfits :-) Any and all feedback is welcome. -Iavor On 5/11/05, Brian Smith <[EMAIL PROTECTED]> wrote: > On 5/10/05, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > The MTL might be deprecated soon, > > replaced by Iavor's library, for example. > > Hi, > > Is this just a rumor, or is this really the plan? Where is the best place > to get lavor's library? > > Thanks, > Brian Smith > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > > ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
[EMAIL PROTECTED] wrote: Jacques Carette writes: > Jerzy Karczmarczuk wrote: >> Syntax for 3D arrays? >> Give me one single language where this is natural and immediate. > > I can think of 3: Mathematica, Maple and APL. I can't see how Maple makes things more *natural and immediate* than Matlab *in this context*. I claim that Maple (and Mathematica) are as natural and immediate as Matlab in the context of 2D arrays and matrices, and that (at least) Maple is more natural for n-dimensional arrays. Maple is rich, there are arrays, Arrays, Matrices (which are *not* multi- dimensional, only two), etc., based on rtables. In which sense rtables are more natural and immediate than multidim matrices in Matlab? Indexing is similar (Maple has a full plethora of adjustable indexing functions, but Matlab can achieve the same with the OO layer). You have put your finger on the reason: Maple's indexing into all objects that are an occurence of the family of "rectangular tables" (ie where the implementation data-structure is an rtable even though the abstract type might be Vector or Matrix or ...) is completely uniform, regardless of dimension. In Matlab, you have no such abstract uniform interface - you have to build it yourself. I have not looked too closely, but it appears that Mathematica offers something equivalent to Maple in this regard. Matlab's weakness here is that the implementation (array) and the Abstract Data Type of a matrix are confounded into one. In Maple, these are separate, with proper interfaces. Of course, since it is Maple, users still have 100% access to the underlying implementation, for good or ill. [Talk about initialization options] Why this is better than in Matlab? I should have been clearer: I only claim at least as good as Matlab, with definite sub-cases where it is better. > Furthermore, for 'structured' matrices (including sparse), there are > simple examples where both Mathematica and Maple are arbitrarily faster > than Matlab on LU and QR decompositions, as well as Eigenvalue > computations. I would like to see some comparisons. Not that I don't believe you, but Matlab made some progress as well I don't have the time to get into detailed comparisons - and much to my horror, the internal white papers where lots of the leg work of doing these comparisons were never made public! Here is a benchmark to try: [Creates a random 3 by 3 matrix mb but with a banded 30-30 structure, a random 10 vector v and solves mb*x = b. Timing done on my slow Celeron laptop] with(LinearAlgebra): N:=3: (bl,bu):=30,30: mb := RandomMatrix(N,outputoptions=[datatype=float,shape=band[bl,bu]]): v := RandomVector(N,outputoptions=[datatype=float]): infolevel[LinearAlgebra]:=2: st:=time(): LinearSolve(mb,v): time()-st; LinearSolve: "using method" LU LinearSolve: "calling external function" LinearSolve: "CLAPACK" hw_dgbtrf_ LinearSolve: "CLAPACK" hw_dgbtrs_ 1.062 [that is 1.062 seconds!] Unless you have 6.8 Gigabytes of main memory on your computer, I would not attempt this in Matlab. (although all this "progress" is sometimes dubious, with the slowing-down of the interface, regression bugs, etc.; no system is ideal, Maple neither). All the mathematical systems suffer greatly (Maple included) from such extremely dubious "progress". I find the new Maple interface close to unusable [luckily for me, work on that started after I had left the company ;-) ]. The point I am trying to make is that being able to use extremely complex 'types' (like a Matrix has a band structure) is what allows Maple to beat Matlab. And the proper use of concepts like ADTs and interfaces makes it easy to write uniform code even if the underlying 'type' varies greatly [There are 13 different internal rtable representations in Maple, not counting indexing functions, orientation, type-representation, etc -- but this is invisible to the user]. The big pain with Maple is that it is dynamically typed (this is Haskell-cafe after all!). On the other hand, things like 'this is a banded(30,30) 3x3 matrix' still seem to be out of reach of Haskell [because the tricks I have seen to encode numbers into types all make encoding the number 3 completely unpalatable]. Jacques ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
Tim Rowe writes: On 5/11/05, Jerzy Karczmarczuk <[EMAIL PROTECTED]> wrote: Give me one single language where [3-d arrays are] natural and immediate. I don't know how Matlab does it, but I find the C++ standard library vector > > entirely intuitive (apart, perhaps, for the need for those two spaces)! Let's precise what I consider to be important in order to call it natural and immediate. And, in general, useful. 1. The definition of a concrete object, not just its type, but, say, the initialization with constants. Or/and, global initialization with zeros. 2. Easy synthesis of multi-dim matrices out of "planes", of submatrices of lesser dimensions; it can be an 'overlay', like, say, making a colour image out of three R/G/B planes, or making a 3D surfaces, or aking tensors through external products. 3. Easy indexing, and not only A[i][j][k], etc., but slicing, the extraction of sub-dimensional matrices, e.g., one column vector out of a 2D matrix in Matlab: A(3,:). Also, extracting parts (e.g. sub-images). Also, in mathematical context, "intelligent" indexing, e.g. treating a matrix as implicitly anti-symmetric. Here the CAS systems as Maple or Mathematica provide the adequate tools. C++ of course doesn't, unless you overload [] yourself. 4. Readable iterators, perhaps something more compact than insipid do-loops. 5. If those matrices are used as mathematical objects: tensors, etc., I want to have some simple notation for inner multiplications/ contractions, etc. This is not just the syntax problem, but the existence of good libraries as well... 6. Reshaping of those arrays. I thought that Matlab 'reshape' (or something similar in Numeric Python) is a baroque, rarely used construction. Now I use it quite often... So, plenty of things. That's why this is not so trivial... Jerzy Karczmarczuk ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Tables in Haskell (data model /business app pr ototyping)
> From: Rene de Visser [mailto:[EMAIL PROTECTED] > > >What do you mean by "external" database? If you just mean "on another > > I would like to write my views and constraints in Haskell, > and not in a > seperate database language. > > i.e. I want to use Haskell also as declarative active > database language to > define the business logic and rules. This would seem to me > to be a lot > easier when the database is written in Haskell itself and > part of the same > program. > > Rene. Well, in that case, HaskellDB is probably about as good as it's gonna get. Were you looking for something similar to an existing system that you're familiar with? (Datalog? Kliesli?) Alistair. - * Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. * ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
Samuel Bronson writes about Matlab: I had to use it a bit for a class and it was *PURE PAIN* beyond the simplest of things. With my full respect, this is your problem. My students, with some guidance, managed to implement a small automatic differentiation package in it, and they are still alive and happy. Another team worked on physical models of musical instruments, and they finished the project without trying to murder anybody. Syntax for 3D arrays? Give me one single language where this is natural and immediate. Numerical Python! Yes, the syntax is Python's, but the syntax doesn't really do much of anything unless you use it with Numeric. Anyway, the syntax is quite uniform and general. You can use it for any number of dimensions (including 0!). I used NumPy quite recently (with PIL, for image processing; actually this was a pedagogical attempt to reimplement my old Clean package Clastic using a vector language, not a functional one. This worked, moreover NumPy is free.) So I second your good opinion of Numerical Python, although the story of two not-so compatible implementations, the old NumPy (or Numeric) and NumArray is a bit annoying. But why we have used it? BECAUSE it is similar to Matlab, in fact cloned somehow *after it...*, the whole idea of Ufuncs is based on Matlab. So, please, let me keep my previous opinion that it is not easy to find something explicitly better than Matlab or its clones in the discussed context. It is obviously my personal impression, I won't convert anybody, but I will defend my standpoint. Jerzy Karczmarczuk ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] NumberTheory library
On 5/10/05, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > The MTL might be deprecated soon, > replaced by Iavor's library, for example. Hi, Is this just a rumor, or is this really the plan? Where is the best place to get lavor's library? Thanks, Brian Smith___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell-Cafe Digest, Vol 21, Issue 27
On 11/05/05, Stijn De Saeger <[EMAIL PROTECTED]> wrote: > Quinn Dunkan <[EMAIL PROTECTED]> wrote : > > > ... It is very natural to > > write in a somewhat functional style, especially in regards to > > sequence processing: higher order functions and listcomps provide the > > processing and its built in generators and iterator protocol provide > > some of the benefits of laziness. Its elementary pattern matching > > encourages you to return as many values from a function as you need > > and use zip() (another haskell steal) to iterate over parallel > > sequences (all pattern matches are irrefutable, though). > > I'm confused... Python has pattern matching ? Well, we usually call it unpacking. You can only do it on sequences (maybe just tuples?), it looks like this: (x, y) = (1, 2) or this: x, y = 1, 2 -- Sam ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
On 11/05/05, Jerzy Karczmarczuk <[EMAIL PROTECTED]> wrote: > Michael Vanier comments my defense of Matlab: > > >>I used objects, and even a lot of functional > >>constructs. I don't see any reason to call it a creeping horror. > >>It is quite homogeneous and simple, and is decently interfaced. > >> > >> > >> > > > >It's incredibly inconsistent. To cite just one example, the syntax is > >geared towards the notion that "everything is a two-dimensional matrices of > >double-precision floating point numbers". If you want to have a > >three-dimensional array, you can do that, but the syntax is not going to be > >nearly as elegant, because matlab's array syntax doesn't scale at all. > > > Come on... > Matlab has cells and the full object-oriented layer nowadays. There > are short ints, strings, complex numbers, etc. The extensibility is > good. The overall consistency is reasonable. I had to use it a bit for a class and it was *PURE PAIN* beyond the simplest of things. > Syntax for 3D arrays? > Give me one single language where this is natural and immediate. Numerical Python! Yes, the syntax is Python's, but the syntax doesn't really do much of anything unless you use it with Numeric. Anyway, the syntax is quite uniform and general. You can use it for any number of dimensions (including 0!). -- Sam ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
On Wed, 11 May 2005, Jerzy Karczmarczuk wrote:
> Pierre Barbier de Reuille wrote about Python and lambdas:
>> Well, I would not recommand using lambda functions ! The main reason
>> is they are limited in that they only accept expressions (ie. not
>> statements) and you can end up with very ugly things (mainly because
>> of the lack of if-expressions).
>
> Oh! You would *like to have imperative statements within LAMBDA*?
>
> Friend, you are in state of mortal sin!
>
> I suppose that if somebody decides to use lambdas, he wants to do some
> functional programming, no?
Debatable.
> True, there are no conditional expressions. But there are because of the
> laziness of boolean combinators. This works:
>
> (x > y) or 'allez en enfer'
Yes, and hallelujah, there are other options too -- suppose we
define a helper function (because "exec" is also a statement)
to execute a compiled code object:
def ex(st, env):
exec(compile(st, '', 'single'), env)
Now we can use this function to compile and execute anything we
like from inside the lambda!
five = lambda x: ex('if x == 5:\n\tprint "five"\nelse:\n\tprint "not
five"', locals())
Donn
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Re: [Haskell-cafe] Python?
Jacques Carette writes: Jerzy Karczmarczuk wrote: Syntax for 3D arrays? Give me one single language where this is natural and immediate. I can think of 3: Mathematica, Maple and APL. Well, you are the village specialist on Maple here,so I won't argue too long, but kill me, I can't see how Maple makes things more *natural and immediate* than Matlab *in this context*. Maple is rich, there are arrays, Arrays, Matrices (which are *not* multi- dimensional, only two), etc., based on rtables. In which sense rtables are more natural and immediate than multidim matrices in Matlab? Indexing is similar (Maple has a full plethora of adjustable indexing functions, but Matlab can achieve the same with the OO layer). Initialization, hmmm, in Maple there are nested lists, in Matlab it is a bit awkward, but with 'cat' along any dimension this is not so bad. What else? Maple is more rich and more complicated, so it has more potential 'power', but that wasn't my point. Mathematica,... well it has nested lists called Array, or Table, or Matrix (which doesn't seem to be more than 2-dim either). Why this is better than in Matlab? -- ... from a "normal" user perspective if possible. For such a user APL doesn't seem to be a popular option, so let's forget it, although it is a respectable part of history of programming languages. == Furthermore, for 'structured' matrices (including sparse), there are simple examples where both Mathematica and Maple are arbitrarily faster than Matlab on LU and QR decompositions, as well as Eigenvalue computations. While Mathematica and Maple used to be pathetic at numeric computations, that has changed a lot in the last 5 years. I would like to see some comparisons. Not that I don't believe you, but Matlab made some progress as well (although all this "progress" is sometimes dubious, with the slowing-down of the interface, regression bugs, etc.; no system is ideal, Maple neither). Jerzy Karczmarczuk ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
Jerzy Karczmarczuk a écrit : Pierre Barbier de Reuille wrote about Python and lambdas: Well, I would not recommand using lambda functions ! The main reason is they are limited in that they only accept expressions (ie. not statements) and you can end up with very ugly things (mainly because of the lack of if-expressions). Oh! You would *like to have imperative statements within LAMBDA*? Friend, you are in state of mortal sin! I suppose that if somebody decides to use lambdas, he wants to do some functional programming, no? True, there are no conditional expressions. But there are because of the laziness of boolean combinators. This works: (x > y) or 'allez en enfer' That's not my point ! I'm only saying there is no if-expression ... so you _need_ statements. And if you really want to use lazy boolean operators, you'll end up having very ugly code replacing tests ... Pierre Jerzy Karczmarczuk ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Pierre Barbier de Reuille INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP Botanique et Bio-informatique de l'Architecture des Plantes TA40/PSII, Boulevard de la Lironde 34398 MONTPELLIER CEDEX 5, France tel : (33) 4 67 61 65 77fax : (33) 4 67 61 56 68 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] and what about AliceML?
fred wrote: As long as this group seems to tolerate "What about Haskell and language X?" As an aside... This group has been extremely tolerant of my newbie questions. I do want to say thank-you to everyone who has been explaining things to me. I've learned quite a bit about programming languages the last couple of weeks. Just as importantly, I understand better why Haskell rocks, and when it is appropriate to use. has anyone had any experience with AliceML? My initial impression is that it might be a nice tool for teaching fundamental concepts. I'd be interested to know too. Cheers, Daniel. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] and what about AliceML?
Hi, As long as this group seems to tolerate "What about Haskell and language X?" has anyone had any experience with AliceML? My initial impression is that it might be a nice tool for teaching fundamental concepts. ---fred ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Type classes and definite types
Hi Bryn Keller, The solution for your problem is very simple. You just have to fetch all values as strings. In this way the library will do all required conversions for you. printRow stmt = do id <- getFieldValue stmt "ID" code <- getFieldValue stmt "Code" name <- getFieldValue stmt "Name" putStrLn (unwords [id, code, name]) Cheers, Krasimir On 5/6/05, Bryn Keller <[EMAIL PROTECTED]> wrote: > Max Vasin wrote: > > >Bryn Keller <[EMAIL PROTECTED]> writes: > > > > > > > >>Hi Max, > >> > >> > >Hello Bryn, > > > > > > > >>Thanks for pointing this out. It's odd that I don't see that anywhere > >>in the docs at the HToolkit site: > >>http://htoolkit.sourceforge.net/doc/hsql/Database.HSQL.html but GHC > >>certainly believes it exists. However, this doesn't actually solve the > >>problem. Substituting toSqlValue for show in printRow' gives the same > >>compile error: > >> > >>Main.hs:22:18: > >>Ambiguous type variable `a' in the constraint: > >> `SqlBind a' arising from use of `getFieldValue' at Main.hs:22:18-30 > >>Probable fix: add a type signature that fixes these type variable(s) > >> > >>So, like with (show (read s)), we still can't use the function until > >>we've established a definite type for the value, not just a type > >>class. > >> > >> > >Yeah... > >Some more RTFSing shows that we have the > > > >getFieldValueType :: Statement -> String -> (SqlType, Bool) > > > >which allows us to write > > > >printRow stmt = do (id :: Int) <- getFieldValue stmt "ID" > > let (codeType, _) = getFieldValueType stmt "Code" > > codestr <- case codeType of > > SqlChar _ -> do (c :: String) <- > > getFieldValue stmt "Code" > > return (toSqlValue c) > > SqlInteger -> do (i :: Int) <- > > getFieldValue stmt "Code" > >return (toSqlValue i) > > -- etc for all SqlType data constructors > > putStrLn (unwords [show id, codestr]) > > > >At least it compiles. But it's ugly :-( > > > > > Ah, good point! Ugly it may be, but at least it works. Thanks for the idea! > > Bryn > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] Python?
Hello Jerzy, Wednesday, May 11, 2005, 3:40:51 PM, you wrote: JK> I suppose that if somebody decides to use lambdas, he wants to do some JK> functional programming, no? well, i am use this all the way :) simplified example of one usage: (allocate, shrink) <- memoryAllocator buf size (buf,size) <- allocate 65536 ... shrink buf realsize another example: compress read_f write_f = do buf <- malloc 65536 let go = len <- read_f buf 65536 when (len>0) $ do ... write_f outbuf outlen go go and i find this feature very convenient -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Tables in Haskell (data model /business app prototyping)
From: "Bayley, Alistair" <[EMAIL PROTECTED]> > From: Rene de Visser [mailto:[EMAIL PROTECTED] > > I would rather use Haskell also for the persistency, global > constraint > maintanence, etc... rather than using an external database. What do you mean by "external" database? If you just mean "on another I would like to write my views and constraints in Haskell, and not in a seperate database language. i.e. I want to use Haskell also as declarative active database language to define the business logic and rules. This would seem to me to be a lot easier when the database is written in Haskell itself and part of the same program. Rene. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
Jerzy Karczmarczuk <[EMAIL PROTECTED]> wrote: Syntax for 3D arrays? Give me one single language where this is natural and immediate. I can think of 3: Mathematica, Maple and APL. But I hope you don't try to convince us that Mathematica is good at number crunching... For linear algebra, Maple, Mathematica and Matlab all use ATLAS and hardware BLAS (when available). For IVP ODEs, the author of the underlying numerical solver for Matlab and Maple are lead by the same person (Larry Shampine); he has publicly stated that he thinks the one for Maple representes the state-of-the-art [mostly because of access to symbolic differentiation], with the one in Matlab being just a bit behind. Furthermore, for 'structured' matrices (including sparse), there are simple examples where both Mathematica and Maple are arbitrarily faster than Matlab on LU and QR decompositions, as well as Eigenvalue computations. While Mathematica and Maple used to be pathetic at numeric computations, that has changed a lot in the last 5 years. Jacques ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
Quinn Dunkan <[EMAIL PROTECTED]> writes:
> Python has first class functions and lexical scoping, and encourages
> higher-order functions, though to a much lesser degree than a real
> functional language.
It's lexical scoping is limited:
- The syntax can be heavy, as you can't embed a function containing
statements inside an expression.
- Because of implicit variable definitions (and lack of other syntax
which could change that) you can't modify variables introduced by
outer functions.
- Class definitions don't use lexical scoping (definitions introduced
in a class body are not visible as unqualified names by their bodies).
--
__("< Marcin Kowalczyk
\__/ [EMAIL PROTECTED]
^^ http://qrnik.knm.org.pl/~qrczak/
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RE: [Haskell-cafe] Tables in Haskell (data model /business app pr ototyping)
> From: Rene de Visser [mailto:[EMAIL PROTECTED] > > I would rather use Haskell also for the persistency, global > constraint > maintanence, etc... rather than using an external database. > > The only thing I have found so far is HApps, but I haven't > figure out how > that works. > > Is there anything else? What do you mean by "external" database? If you just mean "on another server, accessed via a separately installed library or API" then you should consider Sqlite as a persistence storage solution. It's a doddle to install on common platforms, and consists of a single library which links to your program i.e. it runs in the same process-space. Both HSQL (and therefore HaskellDB, as it uses HSQL) and Takusen support Sqlite. http://haskelldb.sf.net/ http://cvs.sf.net/viewcvs.py/haskell-libs/libs/takusen/ Alistair. - * Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. * ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Tables in Haskell (data model /business app prototyping)
Hello, I have been thinking about using Haskell for prototyping of business apps. I would rather use Haskell also for the persistency, global constraint maintanence, etc... rather than using an external database. The only thing I have found so far is HApps, but I haven't figure out how that works. Is there anything else? I guess I could just use lists for the relations, and the state monad. I would extend the record types witha deleted flag and a transaction number (i.e. simple multi version control). Then updates would just consist of pushing a new record onto the front of the list, and rollbacks and commits come for free. The only disadvantage I see that I always need to scan through the whole list all the time, which will get long, and might even be too slow for prototyping. The lists might also get too large memory wise. Any suggestions? Any libraries? Any experiences with HApps or prototyping business apps with haskell in general? Rene. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
Erik de Castro Lopo wrote: Its good for small scripting tasks. Its good for string processing. I find the dynamic typing a pain. What's dynamic typing? I have a lady friend who wants to learn how to program. I just decided to teach her Python for practical reasons: Its a great first language for people who aren't interested in making a career of programming. But I do hesitate. I would like to teach her Haskell because I think it's a better language. Its a better language for people who either have a computer science background or intend to study computer science. I would not inflict a language like Haskell on someone who just wants to get the job done with as little fuss as possible. Thank you for the info, I really appreciate it. I feel better about Python now. Given my circunstances, do you think that's a reasonable approach for teaching her how to program? Teach her Python. If you try and teach her Haskell she will end up programming in visual basic :-). Heh. Cheers, Daniel. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
Pierre Barbier de Reuille wrote about Python and lambdas: Well, I would not recommand using lambda functions ! The main reason is they are limited in that they only accept expressions (ie. not statements) and you can end up with very ugly things (mainly because of the lack of if-expressions). Oh! You would *like to have imperative statements within LAMBDA*? Friend, you are in state of mortal sin! I suppose that if somebody decides to use lambdas, he wants to do some functional programming, no? True, there are no conditional expressions. But there are because of the laziness of boolean combinators. This works: (x > y) or 'allez en enfer' Jerzy Karczmarczuk ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
Michael Vanier comments my defense of Matlab: I used objects, and even a lot of functional constructs. I don't see any reason to call it a creeping horror. It is quite homogeneous and simple, and is decently interfaced. It's incredibly inconsistent. To cite just one example, the syntax is geared towards the notion that "everything is a two-dimensional matrices of double-precision floating point numbers". If you want to have a three-dimensional array, you can do that, but the syntax is not going to be nearly as elegant, because matlab's array syntax doesn't scale at all. Come on... Matlab has cells and the full object-oriented layer nowadays. There are short ints, strings, complex numbers, etc. The extensibility is good. The overall consistency is reasonable. Syntax for 3D arrays? Give me one single language where this is natural and immediate. We are 2D readers/writers, our way of presenting information is 2D within a text editor, and similar problems hit everywhere. I used 3D matrices for the image synthesis, for colour image processing, for simulations of physical systems. It wasn't worse, and even better than in many other languages. I haven't used matlab seriously for a few years (thankfully), but I vaguely recall several other instances of the same problem. Basically, matlab makes programming very easy within a very restricted domain, but if you want to go outside that domain, you will have to endure a lot of pain. Since you vaguely remember something you are thankfully away from, I believe I can continue to "endure my pain" and I can assure all the other readers of this text from the perspective of somebody who uses Matlab *NOW*, that this "pain" is supportable. Optional smiley. The vectorized "comprehension" expressions are really neat. In contrast, Mathematica has a pretty consistent and elegant language. Since I respect others' religions I won't argue. But I hope you don't try to convince us that Mathematica is good at number crunching... Jerzy Karczmarczuk ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
At 19:02 10/05/05 -0400, Daniel Carrera wrote: Hello, This might be a strange question to ask on a Haskell list, but I do want to hear your opinions. What do you think of Python? I think it's benefits are neatly summed up by this comment from Tim Berners-Lee, "Python is a language you can get into on one battery": [[ By the way... Python is cool. I had lamented that it ws a long time since I had a practial hacking environment, and Dan Connolly suggested Python as something you could start quickly but which would scale to a large system. One day, 15 minutes before I had to leave for the airport, I got my laptop back out of my bag, and sucked off the web the python 1.6 system and the python tutorial, and a copy of a small notation3 parser Dan had hacked together. I was happy to find that Python is a language you can get into on one battery! I have been happily hacking ever since. I remember Guido trying to persuade me to use python as I was trying to persuade him to write web software! ]] -- http://dev.w3.org/cvsweb/2000/10/swap/Overview.html?rev=1.20 I was using Python for much of my work before I came to Haskell. It took me a long time to learn to use Haskell anything like effectively (partly, but not entirely, because I'd been corrupted by years of imperative programming). I now choose Haskell for my work because its greater formality appeals to me for my desired applications, but I still use Python and would probably choose it for the kind of use you propose. To be a "starter language", I think there needs to be some delineation between the simple, obvious concepts of functional programming and the more advanced notions that are needed to build programming frameworks. (cf. my recent posting referring to a comment by Alan Kay and Smalltalk -- http://www.haskell.org//pipermail/haskell-cafe/2005-May/010020.html). I do think that there's a strong role for functional programming for "non-professional" programmers, but I'm not sure that "raw" Haskell is it. I think the Vital project (http://www.cs.kent.ac.uk/projects/vital/) is an interesting take (at the level of function rather than specifically the visual aspects) but (last time I looked) lacks IO capability.) #g Graham Klyne For email: http://www.ninebynine.org/#Contact ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] NumberTheory library
Hi [EMAIL PROTECTED] wrote: G'day all. Quoting Bo Herlin <[EMAIL PROTECTED]>: Great! I like this a LOT. ... I don't know if I count as a guru or not, but by all means. Want to discuss this on-list or off-list? The code kinda big already, 700 lines + an util-file, so i'll put it on-line at http://www.gcab.net/haskell-cafe-table so that we can diskuss it on-list. /Bo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
Daniel Carrera a écrit : Quinn Dunkan wrote: Python has first class functions and lexical scoping, and encourages higher-order functions, though to a much lesser degree than a real functional language. I was surprised to hear about first class functions and higher order functions. So I googled for a bit, and I found something neat: -- # Python implementation of Common Lisp's remove_if def remove_if(predicate, lst): return [elem for elem in lst if not predicate(elem)] print remove_if(lambda x:x % 2, [1,2,3,4,5,6,7,8]) -- This is so cool. So there we have a higher order function, passing a funtion as an argument, and even lambda notation. Neat. Well, I would not recommand using lambda functions ! The main reason is they are limited in that they only accept expressions (ie. not statements) and you can end up with very ugly things (mainly because of the lack of if-expressions). Better use local functions for the same goal ! So your example becomes: >>> def is_even(x): ... return x%2 >>> print remove_if(is_even, [1,2,3,4,5,6,7,8]) Or even better: >>> def is_even(x): ... return x%2 >>> print remove_if(is_even, xrange(1,9)) And as local functions have lexical closure this is very interesting (much more than lambda). It is very natural to write in a somewhat functional style, especially in regards to sequence processing: higher order functions and listcomps provide the processing and its built in generators and iterator protocol provide some of the benefits of laziness. Hhhmmm.. I guess the above is also an example of that. [snip: lots of very interesting info I didn't know about] Thank you for all the information. I learned a lot today. I had no idea that Python had these features. Cheers, Daniel. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Pierre Barbier de Reuille INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP Botanique et Bio-informatique de l'Architecture des Plantes TA40/PSII, Boulevard de la Lironde 34398 MONTPELLIER CEDEX 5, France tel : (33) 4 67 61 65 77fax : (33) 4 67 61 56 68 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Python?
> Date: Wed, 11 May 2005 07:49:38 +0200 > From: Jerzy Karczmarczuk <[EMAIL PROTECTED]> > > Michael Vanier wrote: > > >I have enough problems convincing people to learn Scheme. I've > >even had people beg me to teach them Matlab as a first programming > >language, because that is the only language that they needed to get their > >work done. Telling them that Matlab's programming language is a creeping > >horror doesn't sway them at all. > > > > > Now, why so? > I won't defend the Matlab language too strongly, but I used it > for teaching scientific computations, I exploited the vectorized > expressions, I used objects, and even a lot of functional > constructs. I don't see any reason to call it a creeping horror. > It is quite homogeneous and simple, and is decently interfaced. > > Jerzy Karczmarczuk > It's incredibly inconsistent. To cite just one example, the syntax is geared towards the notion that "everything is a two-dimensional matrices of double-precision floating point numbers". If you want to have a three-dimensional array, you can do that, but the syntax is not going to be nearly as elegant, because matlab's array syntax doesn't scale at all. I haven't used matlab seriously for a few years (thankfully), but I vaguely recall several other instances of the same problem. Basically, matlab makes programming very easy within a very restricted domain, but if you want to go outside that domain, you will have to endure a lot of pain. That is not good language design. In contrast, Mathematica has a pretty consistent and elegant language. Mike ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
