April 2013 - Haskell-Cafe

Haskell training in San Francisco Bay Area and New York
by Duncan Coutts 25 Apr '13

25 Apr '13

Well-Typed are offering Haskell courses in the San Francisco Bay Area and New York in early June. They are for professional developers who want to learn Haskell or improve their skills. There is a 2-day introductory course and a 2-day advanced course. Full course and registration details: http://www.well-typed.com/services_training Well-Typed are running these courses in partnership with FP Complete and Skills Matter. Locations, dates ================ San Francisco Bay Area * Introductory Course: June 4-5th, 2013 * Advanced Course: June 6-7th, 2013 New York * Introductory Course: June 10-11th, 2013 * Advanced Course: June 12-13th, 2013 * Early bird discount before April 29th -- Duncan Coutts, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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Why the `-ghc7.4.2' suffix on *.SO base names?
by Captain Freako 25 Apr '13

25 Apr '13

In trying to compile a 2 year old, previously working project on a new machine with a fresh Haskell Platform installation, I bumped into this: ghc -o libami.so -shared -package parsec -lHSrts -lm -lffi -lrt AMIParse.o AMIModel.o ami_model.o ExmplUsrModel.o Filter.o /usr/bin/ld: /usr/lib/ghc-7.4.2/libHSrts.a(RtsAPI.o): relocation R_X86_64_32S against `ghczmprim_GHCziTypes_Czh_con_info' can not be used when making a shared object; recompile with -fPIC /usr/lib/ghc-7.4.2/libHSrts.a: could not read symbols: Bad value collect2: error: ld returned 1 exit status When I investigated why the *.A, instead of the *.SO, was being picked up, I found that the *.SO had a `-ghc7.4.2' appended to its base name. Is this new? What is its purpose? Do I need to add a `LIB_SUFFIX' variable to my makefile and append it to all of my `-l<...>'s, or is there a more elegant solution? Thanks! -db

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Fwd: How to do automatic reinstall of all dependencies?
by capn.freako＠gmail.com 25 Apr '13

25 Apr '13

-db ----- Forwarded message ----- From: "Captain Freako" <capn.freako(a)gmail.com> Date: Tue, Apr 23, 2013 9:21 pm Subject: How to do automatic reinstall of all dependencies? To: <haskell-cafe(a)haskell.org>

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Re: [Haskell-cafe] Instances for continuation-based FRP
by Conal Elliott 25 Apr '13

25 Apr '13

The intuition intrigues me. If, upon inspection, it survives morphs into something else, I'd like to hear about it. Good luck! -- Conal "The object of mathematical rigor is to sanction and legitimize the conquests of intuition, and there was never any other object for it." - Jacques Hadamard "I call intuition cosmic fishing. You feel a nibble, then you've got to hook the fish." -- Buckminster Fullero On Wed, Apr 24, 2013 at 7:26 PM, earl obscure <theanswertoproblems(a)gmail.com > wrote: > > His description of the different frp approaches starts at section 2.1 of > the thesis. > http://www.testblogpleaseignore.com/wp-content/uploads/2012/04/thesis.pdfTh… in 3.1 describes implementation of discrete signals. I don't think he > gives a denotational semantics. > I was thinking, the event, is the derivative of the specific continuous > signal it corresponds to, all other continuous signals of the system held > equal. Applying the partial derivative, is like sampling, or discrete time > stepping. But it is samplying the entire state, or multivariate structure > not just the specific symbol. This made more sense unarticulated. I'll > need to think a bit.

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Re: [Haskell-cafe] Instances for continuation-based FRP
by Conal Elliott 25 Apr '13

25 Apr '13

Hi Jared, Oh -- does Elm have a denotational semantics? I haven't heard of one. I just now skimmed the informal description of the Signal type<http://elm-lang.org/docs/Signal/Signal.elm>, and from the reference to "updates" in the description of "merge", it sound like whatever semantics it might have, it couldn't be function-of-time. I'm intrigued with your interpretation. I wonder what it could mean for an event to be a derivative, especially partial one, and for arbitrary types. -- Conal On Wed, Apr 24, 2013 at 1:48 PM, earl obscure <theanswertoproblems(a)gmail.com > wrote: > Hi Conal, > > > Caveat pre-emptor I'm new to haskell, frp, etc.... .. anyway how I was > interpreting Elm's Eventbased strict FRP, was that each event was the > partial derivative of the continuous time variable, and then since it was > being strict, it would evaluate the tangent line or state of the system at > that point, only update when necessary. > > > Now related to Continuations, this is something I've been thinking about > as well,but haven't gotten very far; apparently cont monad, and comonad are > closely related. I was hoping to use the comonad rules, extend/duplicate > to encode different continuations paths, and then extract when, a > continuation path is chosen. Was hoping maybe the analog would be PDE's, > or something more general than my interpretation of Elm's FRP. > > These are just random thoughts that I wanted to get out. Thanks. > > Jared Nicholson. > >

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Request for help with shared object link failure, involving relocation and -fPIC.
by Captain Freako 25 Apr '13

25 Apr '13

Can anyone help me solve this link failure? ghc -o libami.so -shared -package parsec -lHSrts -lm -lffi -lrt AMIParse.o AMIModel.o ami_model.o ExmplUsrModel.o Filter.o /usr/bin/ld: /usr/lib/ghc-7.4.2/libHSrts.a(RtsAPI.o): relocation R_X86_64_32S against `ghczmprim_GHCziTypes_Czh_con_info' can not be used when making a shared object; recompile with -fPIC /usr/lib/ghc-7.4.2/libHSrts.a: could not read symbols: Bad value collect2: error: ld returned 1 exit status Thanks! -db

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Re: [Haskell-cafe] Implementing an embedded language that threads a global structure.
by Ian Bloom 24 Apr '13

24 Apr '13

Incidentally I did find a solution that fits into the type system and also produces the correct result. This was done by making the global parameter change type as well at each lambda so that it becomes a function with the same arrity as the term. Unfortunately to evaluate these terms the program needs fork and do redundant work at every application of lam (so it's a major hack), though it does give me some confidence that a real solution is possible perhaps by using dependent types?: ---- lam :: ((g->(g,a)) -> (g->(g',b))) -> (g->(a->g',a->b)) lam = (\ f -> \ g -> (\x -> fst $ (f (\ gv->(gv,x))) g, \y -> snd $ (f (\ gv->(gv,y))) g )) app :: (g->(a->g1,a->b)) -> (g->(g,a)) -> (g->(g1,b)) app = (\ eA eB -> \ gz -> let (gB, fB) = eB gz in let (lgA, lfA) = eA gB in (lgA fB, lfA fB) ) ext :: ((g1,a)->(g2,b))->(g0->(g1,a))->(g0->(g2,b)) ext = \f -> \a -> \g -> f (a g) idCounter :: Num g => (g,a) -> (g, a) idCounter = \(g, x) -> (g+1, x) -- Example terms trmA = lam (\x -> lam (\y -> app x y)) trmB = (lam (\y -> app trmC y)) trmC = (\g -> (\c->g,\c->c+3)) trmD = (\g -> (g,3)) trmE = app trmC trmD trmF = (ext idCounter) trmD trmG = app trmC (app trmC trmF) trmH = app trmC trmE --- Here's my original statement of the problem http://hastebin.com/raw/bewiqihiyo And here's all my code with new, http://hpaste.org/86273 Unfortunately, I don't know of a way to tell the compiler that essentially the variables x and y in the lam function will always be applied to the same value. Unfortunately, I've reached a limit of my understanding of how pairs integrate with the type system in Haskell, I've considered returning something other than a pair from my base function (such as a function) but I have yet to figure that out. Thanks for your insights, Ian Bloom

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ANN: data-textual: Human-friendly textual representations
by Mikhail Vorozhtsov 24 Apr '13

24 Apr '13

Hello lists, I'm pleased to announce the first release of data-textual[1], a library that provides human-friendly counterparts (called Printable/Textual) of the compiler-friendly Show/Read type classes. The library is intended to be used for printing and parsing of non-compound and non-polymorphic compound data (e.g. numbers, network and hardware addresses, date/time, etc). A quick example (vs network-ip[2] library): λ> import Data.Maybe (fromJust) λ> import Data.Textual λ> import Network.IP.Addr λ> let x = fromString "[dead::b:e:e:f]:123" :: Maybe Inet6Addr λ> x Just (InetAddr {inetHost = ip6FromWords 0xdead 0x0 0x0 0x0 0xb 0xe 0xe 0xf, inetPort = 123}) λ> toString (fromJust x) "[dead::b:e:e:f]:123" λ> let y = fromStringAs aNet4Addr "192.168.100.1/24" λ> y Just (netAddr (ip4FromOctets 192 168 100 1) 24) λ> toText (netPrefix $ fromJust y) "192.168.100.0" [1] http://hackage.haskell.org/package/data-textual [2] http://hackage.haskell.org/package/network-ip

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[ANN] New releases of crypto-api, DRBG, commsec, commsec-keyexchange, and cipher-aes128
by Thomas DuBuisson 23 Apr '13

23 Apr '13

All, I have recently released new versions of: - crypto-api[1]: An interface for cryptographic algorithms such as block ciphers, hashes, and secure random number generators. This version includes Klondike's cbcMac and SIV modes of operation - much thanks to his numerous patches. - DRBG[2]: A set of deterministic random bit generators (aka CPRNGs) based on NIST 800-90. - commsec[3]: A communications security package that provides data in transit security using AES-128 GCM without any external, C library, dependencies. - commsec-keyexchange[4]: A key exchange tool that leverages RSA keys to establish connection's for use with the commsec package. - cipher-aes128[5]: A re-packaging of Vincent Hanquez's excellent AES routines. ==Crypto API== Crypto-API was first released in 2010 with an aim of providing an interface useful to consumers of cryptographic algorithms and providers of those algorithms. It includes classes for block, stream, and asymmetric ciphers as well as for random number generators, hashes, and signature algorithms. Recent changes include: - Added SIV and cbcMac thanks to Klondike. NOTE: Some of this code is only conditionally included via a compile time flag due to GHC's slow compilation of the CPoly module. - Moved block cipher modes into the type classes, allowing use of high-speed C or ASM mode implementations. - More generator query methods in the CryptoRandomGen class. - Updated build dependencies - Move operations and expose them from Crypto.Util ==DRBG== DRBG implements the Hash and HMAC based generators specified in NIST SP 800-90. A generator using block ciphers in CTR mode is also provided, but is not based on the special publication. ==CommSec and CommSec-KeyExchange== Together, these packages provide a way to start from shared RSA keys and obtain a thread-safe secure communications channel. A pull-request is currently out to crypto-pubkey-openssh that would allow the reading and use of RSA keys generated by ssh-keygen. These packages aim to be "morally correct" in that they perform the correct operations at an equivalent computational cost of a properly vetted system, but are not themselves vetted for critical use. For small messages, commsec performs faster than the non-threadsafe secure-sockets counterpart. For larger messages the performance is not as competitive due to the GCM routine not being fully optimized. ==cipher-aes128== This package has performance benefits (vs cipher-aes) due to function-pointer rewriting that allows us to avoid excessive checking of the CPU info [6]. This package is hopefully going to be short-lived with the optimizations getting folded into Vincent's 'cipher-aes' once things are mature enough. A windows tester would help. Comments and patches are welcome. Sorry if I forgot to thank anyone who contributed, many of these projects have been neglected and I lose context in the interim. Cheers, Thomas M. DuBuisson [1] http://hackage.haskell.org/package/crypto-api [2] http://hackage.haskell.org/package/DRBG [3] http://hackage.haskell.org/package/commsec [4] http://hackage.haskell.org/package/commsec-keyexchange [5] http://hackage.haskell.org/package/cipher-aes128 [6] https://github.com/vincenthz/hs-cipher-aes/issues/8 - Up to 40% faster for small operations.

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what happened to alexAndPred?
by Johannes Waldmann 23 Apr '13

23 Apr '13

Hi. I have ghc-7.6.3 and alex-3.0.5. When I build https://github.com/jwaldmann/smt-lib it breaks with Language/SMTLIB/Lexer.x:6:5: Not in scope: `alexAndPred'. It was working with alex-2.3.5. I was going t add "Can I constrain the alex version in the cabal file (I recall this is difficult for executables since they're not registered with ghc)" but it wouldn't help since alex-2.3.5 cannot be built with a recent ghc-7.6 because Module `System.IO.Error' does not export `try'. Also, not with ghc-7.4.2 because of dist/build/alex/alex-tmp/Scan.hs:344:17: Illegal bang-pattern (use -XBangPatterns): And not with <= ghc-7.2 because of Linking /tmp/alex-2.3.5-20331/alex-2.3.5/dist/setup/setup ... unrecognized option `--disable-benchmarks'

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