- template-haskell - Haskell.org

is this (.csv) a good task for template-haskell?
by Lloyd Allison 11 Jul '05

11 Jul '05

I'd like to write some Haskell programs to manipulate comma-separated variable, .csv, files from a spreadsheet. The obvious way to start which, for perverse(?) reasons, I do not want to follow is to create a union type e.g. data CSVelement = I int | S string | ... or similar. All the elements of a given column will be of the same type e.g. bool, int, float, string, or a-selection-of-names (e.g. {Lab, Con, LibDem}). (and some columns with missing values). e.g. "Homer",42,67.8,Lab "Paris",,5.5,Con ... I'd like to write some code that 1. takes a quick look at the file, counts the columns, works out the type of each column (including creating data T1 = Lab|Con|LibDem, and using `Maybe' for missing values), 2. creates a tuple-type for a row, e.g. (String, Maybe Int, Float, T1), and adds that type to Reads, Show (and some other stuff), and 3. then gets on with processing the data. Is template-Haskell a good choice for this task and, if so, what is the quickest way to get started? (Or has it been done?) -Lloyd -- Lloyd ALLISON, CSSE, Monash University, Victoria, Australia 3800. web: http://www.csse.monash.edu.au/~lloyd/ tel: +61 3 9905 5205

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RE: [Template-haskell] Splicing bindings
by Simon Peyton-Jones 11 Jul '05

11 Jul '05

Sadly no. Ideally one would like to be able to splice in *any* syntactic construct, but at present implementing each requires separate work in the implementation, and it's especially tricky if the construct can bind things (such as declarations, patterns, and do-statements). Again, you can do it "by steam" using the lower-level constructors... it's just more clumsy. Simon | -----Original Message----- | From: template-haskell-bounces(a)haskell.org [mailto:template-haskell-bounces@haskell.org] On | Behalf Of Mike Gunter | Sent: 13 June 2005 06:24 | To: template-haskell(a)haskell.org | Subject: [Template-haskell] Splicing bindings | | | Is there a way to splice in a | | nm <- m | | binding? I.e., I'd like something along the lines of | mdo | ... | $(defNm nm m) | ... | ... nm ... | ... | | which would expand to | | mdo | ... | nm <- name "nm" m | ... | ... nm ... | ... | | . Is this possible? | | thanks, | mike | _______________________________________________ | template-haskell mailing list | template-haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/template-haskell

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RE: [Template-haskell] Records and generating splices
by Simon Peyton-Jones 11 Jul '05

11 Jul '05

Template Haskell is indeed poorly documented. I keep hoping that someone will undertake the task of writing better documentation, since that is something that doesn't have to be done at GHC HQ. Meanwhile, your best bets are a) the user manual http://www.haskell.org/ghc/docs/latest/html/users_guide/template-haskell .html including the "notes2.ps" pointed to from the user manual, and the original paper b) the Template Haskell mailing list... but no one has replied to your message. You could try ghc-users for a wider audience c) when it comes to the exact name for each constructor and function, you need the online library documentation, but I think you've found that already. It's not clear from your message, but I think you want to do something like what is described in Section 8 of http://research.microsoft.com/~simonpj/tmp/notes2.ps. If so, I'm afraid that isn't implemented yet, and (somewhat to my surprise) no one has been yelling for it. It's not trivial to implement unfortunately. It's also not essential: you can drop down to the explicit-constructor level described in the original paper. Simon | -----Original Message----- | From: template-haskell-bounces(a)haskell.org [mailto:template-haskell-bounces@haskell.org] On | Behalf Of Rene de Visser | Sent: 08 July 2005 13:40 | To: template-haskell(a)haskell.org | Subject: [Template-haskell] Records and generating splices | | Hello, | | In the following code I wish to generate the invidual accessors, i.e. the | add_rel1, add_rel2, etc. | | I have tried using | | test = [| add_rel1 value = modify (\db -> db{ rel1 = Set.insert value (rel1 | db)}) |] | | with some splicing, but it does not seem possible to splice in the rel1 | before the '='. | Also how do I splice in the add_rel1? | | According to the documentation it is only possible to splice in complete | expressions. This seems quite limiting. Does this mean you always have to | construct the expressions by hand? | | The library documention seems very thin. Its hard to tell how to create a | record accessor and setter from the haddock documentation. | | Note that I have no experience with template haskell. | | It would also be nice to generate the type declaration, but I am finding | this even more difficult. | | Can any one provide some example code to do this. | | Rene. | | | {-# OPTIONS -fglasgow-exts #-} | module DataBase where | | import Control.Monad.State | import qualified Data.Set as Set | -- Does this really need to be extensible??? | -- Entries need to be based on sets, or something similar... | data SmallDB = SmallDB { rel1 :: Set.Set String | , rel2 :: Set.Set Integer } deriving Show | | emptyDB = SmallDB Set.empty Set.empty | | add_rel1 :: (MonadState SmallDB m) => String -> m () | add_rel1 value = modify (\db -> db{ rel1 = Set.insert value (rel1 db)}) | | add_rel2 :: (MonadState SmallDB m) => Integer -> m () | add_rel2 value = modify (\db -> db{ rel2 = Set.insert value (rel2 db)}) | | | _______________________________________________ | template-haskell mailing list | template-haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/template-haskell

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Records and generating splices
by Rene de Visser 08 Jul '05

08 Jul '05

Hello, In the following code I wish to generate the invidual accessors, i.e. the add_rel1, add_rel2, etc. I have tried using test = [| add_rel1 value = modify (\db -> db{ rel1 = Set.insert value (rel1 db)}) |] with some splicing, but it does not seem possible to splice in the rel1 before the '='. Also how do I splice in the add_rel1? According to the documentation it is only possible to splice in complete expressions. This seems quite limiting. Does this mean you always have to construct the expressions by hand? The library documention seems very thin. Its hard to tell how to create a record accessor and setter from the haddock documentation. Note that I have no experience with template haskell. It would also be nice to generate the type declaration, but I am finding this even more difficult. Can any one provide some example code to do this. Rene. {-# OPTIONS -fglasgow-exts #-} module DataBase where import Control.Monad.State import qualified Data.Set as Set -- Does this really need to be extensible??? -- Entries need to be based on sets, or something similar... data SmallDB = SmallDB { rel1 :: Set.Set String , rel2 :: Set.Set Integer } deriving Show emptyDB = SmallDB Set.empty Set.empty add_rel1 :: (MonadState SmallDB m) => String -> m () add_rel1 value = modify (\db -> db{ rel1 = Set.insert value (rel1 db)}) add_rel2 :: (MonadState SmallDB m) => Integer -> m () add_rel2 value = modify (\db -> db{ rel2 = Set.insert value (rel2 db)})

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Records and generating splices
by Rene de Visser 08 Jul '05

08 Jul '05

Hello, In the following code I wish to generate the invidual accessors, i.e. the add_rel1, add_rel2, etc. I have tried using test = [| add_rel1 value = modify (\db -> db{ rel1 = Set.insert value (rel1 db)}) |] with some splicing, but it does not seem possible to splice in the rel1 before the '='. Also how do I splice in the add_rel1? According to the documentation it is only possible to splice in complete expressions. This seems quite limiting. Does this mean you always have to construct the expressions by hand? The library documention seems very thin. Its hard to tell how to create a record accessor and setter from the haddock documentation. Note that I have no experience with template haskell. It would also be nice to generate the type declaration, but I am finding this even more difficult. Can any one provide some example code to do this. Rene. {-# OPTIONS -fglasgow-exts #-} module DataBase where import Control.Monad.State import qualified Data.Set as Set -- Does this really need to be extensible??? -- Entries need to be based on sets, or something similar... data SmallDB = SmallDB { rel1 :: Set.Set String , rel2 :: Set.Set Integer } deriving Show emptyDB = SmallDB Set.empty Set.empty add_rel1 :: (MonadState SmallDB m) => String -> m () add_rel1 value = modify (\db -> db{ rel1 = Set.insert value (rel1 db)}) add_rel2 :: (MonadState SmallDB m) => Integer -> m () add_rel2 value = modify (\db -> db{ rel2 = Set.insert value (rel2 db)})

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Avoiding linking final executable to TH
by Einar Karttunen 04 Jul '05

04 Jul '05

Hello Are there currently any plans to avoid linking the final executable with TH? As far as I understand currently the situation is as follows: Module M uses TH code defined in MTH. Module MTH imports TH modules and thus needs to be linked with template-haskell. The simplest way to deal with this could be to use a special compile-time import construct between M and MTH - so that MTH would not need to be linked with M (and thus template-haskell would not be needed either). Are there any plans regarding something like this or an another solution? - Einar Karttunen

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Second MetaOCaml Workshop: Final CFP
by kswadi＠cs.rice.edu 13 Jun '05

13 Jun '05

FINAL CALL FOR PAPERS (DEADLINE EXTENDED) ========================================= The Second MetaOCaml Workshop http://www.metaocaml.org/workshop05 To be held at GPCE'05 (Wednesday Sep 28, 2005, Tallinn, Estonia) MetaOCaml is a multi-stage extension of the widely used functional programming language OCaml. It provides a generic core for expressing macros, staging, and partial evaluation. As such, it also provides unique support for building aspect weavers in a statically typed setting. The workshop is a forum for discussing experience with using MetaOCaml as well as possible future developments for the language. The scope of the workshop includes all aspects of the design, semantics, theory, application, and implementation of MetaOCaml. The workshop welcomes reports on * novel applications (especially interpreters and aspect weavers), * extensions (macros, new language constructs, offshoring translations), * implementation techniques (compilation, RTCG), support (debugging, profiling), * educational use, * basic theory (staging annotations, static typing, static analysis, environment classifiers, etc). Each submission will be reviewed by at least three members of the Program Committee (PC). The PC will work to provide detailed and constructive comments to the authors. The workshop will only have informal proceedings, and is intended to be close in spirit to the Haskell, ML, and Scheme workshops. Based on author requests and PC decisions, authors will be given either 25-minute or 15-minute slots to present their ideas, either of which will be followed by 15 minutes of questions and discussion. At the end of the workshop, one hour will be allocated to an open discussion to review the outcomes of the meeting, and to discuss future challenges and directions for MetaOCaml. Submission: For uniformity, authors are encouraged to use the latest ACM SIGS conference style file (option 1). We also request that submissions be limited to 12 pages in this style. We ask that papers be submitted in PDF or Postscript forms through the online submission page at http://metaocaml.cs.rice.edu/submit.html. Important Dates: Submission deadline (firm): June 24, 2005 until midnight GMT (Please use online form at http://www.metaocaml.org/workshop05) Notification of acceptance: July 11, 2005 Final versions posted at the workshop sites: October 20, 2005 Registration: Registration for the workshop is part of registering for GPCE'05. The event is co-located with TFP 2005 and ICFP 2005, which already provides housing and transportation information. Program Committee: Cristiano Calcagno Imperial College Rowan Davies University of Western Australia Ralf Hinze Universität Bonn Oleg Kiselyov FNMOC, Monterey, CA, USA Christopher League Long Island University Xavier Leroy INRIA, Paris Emir Pasalic Rice University Jeremy Siek Indiana University, Bloomington Yannis Smaragdakis Georgia Tech Kedar Swadi Rice University (Chair) Walid Taha Rice University Stephanie Weirich University of Pennsylvania Hongwei Xi Boston University

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Splicing bindings
by Mike Gunter 13 Jun '05

13 Jun '05

Is there a way to splice in a nm <- m binding? I.e., I'd like something along the lines of mdo ... $(defNm nm m) ... ... nm ... ... which would expand to mdo ... nm <- name "nm" m ... ... nm ... ... . Is this possible? thanks, mike

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mdo support in Template Haskell
by Mike Gunter 12 Jun '05

12 Jun '05

For those trying to decide priorities: I would like to see mdo supported in Template Haskell. Both mdo and TH are useful for DSELs. It's a shame one can't combine them. thanks, mike

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RE: [Template-haskell] TH type not Typeable?
by Simon Peyton-Jones 10 Jun '05

10 Jun '05

Perhaps someone can go ahead and add these instances to the TH types? Ian? that way it'll be in the next release, at least Simon | -----Original Message----- | From: template-haskell-bounces(a)haskell.org [mailto:template-haskell-bounces@haskell.org] On | Behalf Of Sean Seefried | Sent: 10 June 2005 04:02 | To: Abraham Egnor | Cc: template-haskell(a)haskell.org | Subject: Re: [Template-haskell] TH type not Typeable? | | | On 10/06/2005, at 10:07 AM, Abraham Egnor wrote: | | > I'd just like to pipe up and say that the lack of Typeable and Data | > instances for the TH types has frustrated me as well. | | Me too. But there's a solution. Check out the code that comes with | the third paper in the "Scrap Your Boilerplate" series. There's a | module in there called Derive.hs that contains code for deriving | Typeable and Data instances using Template Haskell. The cool thing | is, you can use it *on* Template Haskell's data types too. | | In fact, I did this in my PanTHeon project available from my web site | at: | | http://www.cse.unsw.edu.au/~sseefried/pantheon.html | | However, this uses an older version of the deriving code. You'd | probably want to get the latest. | | Cheers, | | Sean | _______________________________________________ | template-haskell mailing list | template-haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/template-haskell

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