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Need urgent help with Network.tls
by C K Kashyap 24 Feb '13

24 Feb '13

Hi, I am trying to use Haskell to download email/attachments from gmail. For which I am exploring Network.TLS. I got this sample from the net that connects to gmail smtp and works just fine - http://hpaste.org/82890 However, when I modify it a bit to try to connect to imap, it simply does not work. To debug, I tried to connect to a webserver, even that seems to not work. I modified the function as follows. emailGmail2 = do let host = "localhost" let port = 443 let params = defaultParamsClient{pCiphers = ciphers} g <- RNG.makeSystem h <- connectTo host (PortNumber (fromIntegral port)) hSetBuffering h LineBuffering cWrite h "GET / HTTP/1.0" cWrite h "" cWaitFor h "ABCD" con <- contextNewOnHandle h params g handshake con bye con And I get a "BAD request" response from the server - Can some please give me a sample code that uses Network.TLS to connect to a imap.google.com (or even a webserver for that matter)? Regards, Kashyap

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Re: [Haskell-cafe] Type checking the content of a string
by Corentin Dupont 23 Feb '13

23 Feb '13

Finally, I solved the problem using typeOf instead of interpret: cr :: QuasiQuoter cr = QuasiQuoter { quoteExp = quoteRuleFunc} quoteRuleFunc :: String -> Q TH.Exp quoteRuleFunc s = do res <- runIO $ runInterpreter $ do setImports ["Prelude", "Language.Nomyx.Expression"] typeOf s case res of Right "RuleFunc" -> [| s |] Right _ -> fail $ "Rule doesn't typecheck" Left e -> fail $ show e I don't know really why, but now it's working very well! On Sat, Feb 23, 2013 at 7:56 PM, Daniel Gorín <jcpetruzza(a)gmail.com> wrote: > Hi Corentin, > > I've never used TH, but from what I understand, trying to combine hint and > TH would be redundant (even if it worked): whatever String you can evaluate > using hint, you can evaluate it directly in TH. Is this not the case? > > Cheers, > Daniel > > On Feb 23, 2013, at 6:53 PM, Corentin Dupont wrote: > > > Hi Daniel, > > Did you already tried to use Hint in a QuasiQuote? This would come handy > to check at compile time the validity of some strings... > > However I have the error hereunder. > > The duplicate symbol found in the object file is in fact the first > symbol in this file. So I guess GHCi tries to load it twice... > > Best, > > Corentin > > > > > > On Sat, Feb 23, 2013 at 12:03 AM, Corentin Dupont < > corentin.dupont(a)gmail.com> wrote: > > I'm trying to load my interpreter in the Q monad: > > > > cr :: QuasiQuoter > > cr = QuasiQuoter { quoteExp = quoteRuleFunc} > > > > quoteRuleFunc :: String -> Q TH.Exp > > quoteRuleFunc s = do > > res <- runIO $ runInterpreter $ do > > setImports ["Prelude", "Language.Nomyx.Rule", > "Language.Nomyx.Expression", "Language.Nomyx.Test", > > "Language.Nomyx.Examples", "GHC.Base", "Data.Maybe"] > > interpret s (as :: RuleFunc) > > case res of > > Right _ -> [| s |] > > Left e -> fail $ show e > > > > > > However, I always obtain an error during compilation: > > > > ... > > Loading package XXX ... linking ... done. > > > > > > GHCi runtime linker: fatal error: I found a duplicate definition for > symbol > > __stginit_ghczm7zi4zi1_DsMeta > > whilst processing object file > > /usr/lib/ghc/ghc-7.4.1/libHSghc-7.4.1.a > > This could be caused by: > > * Loading two different object files which export the same symbol > > * Specifying the same object file twice on the GHCi command line > > * An incorrect `package.conf' entry, causing some object to be > > loaded twice. > > GHCi cannot safely continue in this situation. Exiting now. Sorry. > > > > > > I vaguely understand that the interpreted modules are conflicting with > the compiled ones... > > > > > > > > On Fri, Feb 22, 2013 at 11:51 PM, Corentin Dupont < > corentin.dupont(a)gmail.com> wrote: > > Great! That seems very powerful. So you can do what you want during > compilation, readin files, send data over the network? > > Other question, in my example how can I halt the compilation if a test > program is wrong? > > > > > > On Fri, Feb 22, 2013 at 8:30 PM, Francesco Mazzoli <f(a)mazzo.li> wrote: > > At Fri, 22 Feb 2013 19:43:51 +0100, > > Corentin Dupont wrote: > > > Hi Adam, > > > that looks interresting. I'm totally new to TH and QuasiQuotes, though. > > > Can I run IO in a QuasiQuoter? I can run my own interpreter. > > > > Yes, you can: > > < > http://hackage.haskell.org/packages/archive/template-haskell/2.8.0.0/doc/ht… > >. > > > > Francesco > > > > > > > >

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Type checking the content of a string
by Corentin Dupont 23 Feb '13

23 Feb '13

Hi all, I have a program able to read another program as a string, and interpret it (using Hint). I'd like to make unit tests, so I have a file "Test.hs" containing a serie of test programs as strings. However, how could I be sure that these test program are syntactically valid, at compile time? Those programs should have the type "RuleFunc". I tried some TH: printProg :: Q Exp -> String printProg p = unsafePerformIO $ do expr <- runQ p return $ pprint expr myTest = printProg [| <my test program> :: RuleFunc |] But it's not very satisfatory yet. When pretty printing TH changes the program quite a bit and my interpreter cannot compile it due to scoping problems. I'd like to have my test program copied back as is. Is it possible? Any other solutions? Thanks a lot! Corentin

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ANN: data-fix-cse -- Common subexpression elimination for EDSLs
by Anton Kholomiov 23 Feb '13

23 Feb '13

I'm glad to announce the package for Common subexpression elimination [1]. It's an implementation of the hashconsig algorithm as described in the paper 'Implementing Explicit and Finding Implicit Sharing in EDSLs' by Oleg Kiselyov. Main point of the library is to define this algorithm in the most generic way. You can define the AST for your DSL as fixpoint type[2]. And then all you need to use the library is to define the instance for type class `Traversable`. This idea is inspired by `data-reify` [3] package which you can use to transform your ASTs to DAGs too. But it relies on inspection of the references for values when `data-fix-cse` doesn't sacrifices the purity. A short example: Let's define a tiny DSL for signals import Data.Fix type Name = String type E = Fix Exp data Exp a = Const Double | ReadPort Name | Tfm Name [a] | Mix a a deriving (Show, Eq, Ord) We can make constant signals, read them from some ports and transform them (apply some named function to the list of signals) and mix two signals. Let's define an instance of the Traversable (hence for the Functor and Foldable) import Control.Applicative import Data.Monoid import Data.Traversable import Data.Foldable instance Functor Exp where fmap f x = case x of Const d -> Const d ReadPort n -> ReadPort n Mix a b -> Mix (f a) (f b) Tfm n as -> Tfm n $ fmap f as instance Foldable Exp where foldMap f x = case x of Mix a b -> f a <> f b Tfm n as -> mconcat $ fmap f as _ -> mempty instance Traversable Exp where traverse f x = case x of Mix a b -> Mix <$> f a <*> f b Tfm n as -> Tfm n <$> traverse f as a -> pure a Now we can use the functio `cse` cse :: (Eq<http://hackage.haskell.org/packages/archive/base/4.6.0.1/doc/html/Data-Eq.h…>(f Int<http://hackage.haskell.org/packages/archive/base/4.6.0.1/doc/html/Data-Int.…>), Ord<http://hackage.haskell.org/packages/archive/base/4.6.0.1/doc/html/Data-Ord.…>(f Int<http://hackage.haskell.org/packages/archive/base/4.6.0.1/doc/html/Data-Int.…>), Traversable<http://hackage.haskell.org/packages/archive/base/4.6.0.1/doc/html/Data-Trav…>f) => Fix<http://hackage.haskell.org/packages/archive/data-fix/0.0.1/doc/html/Data-Fi…>f -> Dag<http://hackage.haskell.org/packages/archive/data-fix-cse/0.0.1/doc/html/Dat…>f to transform our AST to DAG. DAG is already sorted. Later we can define a handy wrapper to hide the details from the client newtype Sig = Sig { unSig :: E } You can find examples in the package archive Extra-Source-Files: test/Exp.hs test/Impl.hs test/Expl.hs If you want to see a real world example of usage you can find it in the csound-expression[4]. An edsl for the Csound language. One side-note form my experience: Fixpoint types can be very flexible. It's easy to compose them. If suddenly we need to add some extra data to all cases from the example above we can easily do it with just another Functor: Imagine that we want to use a SampleRate value with all signals. Then we can do it like this: type E = Fix SampledExp data SampledExp a = SampledExp SampleRate (Exp a) then we should define an instance of the type class Traversable for our new type SampleRate. The Exp doesn't change. [1] http://hackage.haskell.org/package/data-fix-cse-0.0.1 [2] http://hackage.haskell.org/package/data-fix-0.0.1 [3] http://hackage.haskell.org/package/data-reify [4] http://hackage.haskell.org/package/csound-expression Anton

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Parsec without data declarations/AST
by Sean Cormican 22 Feb '13

22 Feb '13

I have been trying to create a parser for a functional programming language, but there is no need to create an AST but merely check that the code is valid according to the grammar. In the following tutorial I have been trying to take some pointers from, data declarations are used to create an AST for the language, There is, as I understand a way to parse the language without an AST. http://www.haskell.org/haskellwiki/Parsing_a_simple_imperative_language My question is what should the type signatures for example parseFile function instead of "Stmt" accept as input if the parser is to accept Strings and numerical expressions alike ? Thanks for any help, Seán

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question about: --hyperlink-source
by Doaitse Swierstra 22 Feb '13

22 Feb '13

I ran into the problem that for the packages which I install using cabal install The generated html does not contain links to the sources. This issue was raised before in: http://stackoverflow.com/questions/1587635/haddock-for-cabal-installed-modu… I have been looking into the documentation available, but could not find a way to set this e.g. as a default in some .haddock file. Am I overlooking something? Doaitse

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How to input Unicode string in Haskell program?
by Semyon Kholodnov 22 Feb '13

22 Feb '13

Imagine we have this simple program: module Main(main) where main = do x <- getLine putStrLn x Now I want to run it somehow, enter "résumé 履歴書 резюме" and see this string printed back as "résumé 履歴書 резюме". Now, the first problem is that my computer runs Windows, which means that I can't use ghci ":main" or result of "ghc main.hs" to enter such an outrageous string — Windows console is locked to one specific local code page, and no codepage contains Latin-1, Cyrillic and Kanji symbols at the same time. But there is also WinGHCi. So I do ":main", copy-paste this string into the window (It works! Because Windows has Unicode for 20 years now), but the output is all messed up. In a rather curious way, actually: the input string is converted to UTF-8 byte string, and its bytes are treated as being characters from my local code page. So, it appears that I have no way to enter Unicode strings into my Haskell programs by hands, I should read them from files. That's sad, and I refuse to think I am the first one with such a problem, so I assume there is a solution/workaround. Now would someone please tell me this solution? Except from "Just stick to 127 letters of ASCII", of course.

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ANNOUNCE: smallcheck-1.0
by Roman Cheplyaka 22 Feb '13

22 Feb '13

I am glad to announce a new major release of SmallCheck, a property-based testing library for Haskell. The major changes in this release are documented here: http://ro-che.info/articles/2013-02-19-smallcheck.html Roman

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Is the haksell-pkg-janitors group on github alive?
by Jan Stolarek 22 Feb '13

22 Feb '13

Does anyone know if haksell-pkg-janitors group on github is alive? I've submitted a pull request a week ago but no response so far. Janek

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GHC panicking when using -fext-core -O2
by Christian Gosch 21 Feb '13

21 Feb '13

Hi Cafe, when I try to create core files with the above options, ghc panics with this message: ghc: panic! (the 'impossible' happened) (GHC version 7.6.2 for x86_64-unknown-linux): make_exp (App _ (Coercion _)) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug I tried this with 7.4.1 and with 7.6.2. Does anyone have an idea why this could happen, without looking at the code I am trying to compile? Thanks for any hint, Christian

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