- Haskell-Cafe - Haskell.org

some questions about Template Haskell
by TP 30 Jun '13

30 Jun '13

Hi everybody, I am trying to learn Template Haskell, and I have two independent questions. 1/ First, the following code (which is not in its final version, but it is a test) does not compile: ------------------- {-# LANGUAGE TemplateHaskell #-} module Pr where import Language.Haskell.TH pr :: Name -> ExpQ pr n = [| putStrLn $ (nameBase n) ++ " = " ++ show $(varE n) |] ------------------- I obtain: ------------------- No instance for (Lift Name) arising from a use of `n' Possible fix: add an instance declaration for (Lift Name) In the first argument of `nameBase', namely `n' ------------------- Why? Indeed, there is no typeclass constraint on n in the definition of nameBase: ghci> :t nameBase nameBase :: Name -> String Contrary to lift for example: ghci> :t lift lift :: Lift t => t -> Q Exp 2/ If I define in a module: j = 3 and then define in another module: ------------------- h x = $([|j|]) main = do print $ h undefined ------------------- I obtain "3" as expected. However, I do not achieve to make this system work with an infix declaration: infix $([| j |]) + I obtain: parse error on input `$(' What is the problem? Thanks in advance, TP

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Subclass or no subclass?
by Patrick Browne 29 Jun '13

29 Jun '13

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Improving GHC's LLVM Backend
by Alex Ford 29 Jun '13

29 Jun '13

Hello, I'm interested in improving the LLVM backend of GHC by using the existing Haskell LLVM bindings to the C API, as suggested by option 1 in the LLVM FAQ: http://llvm.org/docs/FAQ.html#i-d-like-to-write-a-self-hosting-llvm-compile… At the moment, the backend uses the option 2: emitting LLVM assembly code which is then assembled to LLVM bitcode, optimised, and compiled to machine code by standard LLVM tools. Changing this to use the Haskell FFI bindings to the LLVM C API would allow better tracking of any changes to the LLVM IR, and hopefully a reasonable speed increase by avoiding the overhead of first emitting LLVM Assembly to be assembled. In his bachelor's thesis, David Terei considered this approach when initially writing the LLVM backend, but dismissed it due to the existing Haskell bindings being too large and high level to use with GHC. I have not personally looked at the high level Haskell bindings in much depth, but the low level (llvm-base) bindings appear to be somewhat incomplete with respect to LLVM 3.3. Therefore, I plan to extend the FFI bindings to cover more or all of the C API, and then to modify the GHC LLVM backend to use these bindings to call into the LLVM libraries directly. http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/Backends/LLVMc… a link to David's thesis, as well as documentation of the LLVM backend. I'd really appreciate it if anyone who knows about the Haskell LLVM bindings or about the GHC LLVM backend could give any advice regarding what sort of work needs to be done with the LLVM bindings to make them more appropriate for use within GHC, or how to approach modifying the existing LLVM backend. Many thanks, Alex

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Re: [Haskell-cafe] LLVM Backend status
by JP＠eukor.com 29 Jun '13

29 Jun '13

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LLVM Backend status
by B B 29 Jun '13

29 Jun '13

Hi! I'm new to Haskell and I'm very interested in using it as a base layer for my application. I need to generate the LLVM-IR code from ghc compiler, so I've got 2 questuions to you: 1) Is the LLVM Backend actively developed or should I be afraid it will be discontinued or broken? 2) How can I generate the LLVM IR (or bc) files from the compiler? I see that durign compilation with -fllvm -v3 flags the bc files are created but they are immidietly (after usage) deleted - Is it possible to tell the compiler not to delete them?

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Who uses Travis CI and can help write a cookbook for those guys?
by Ryan Newton 29 Jun '13

29 Jun '13

The Travis folks have decided they want to support Haskell better (multiple compiler versions): https://github.com/travis-ci/travis-ci/issues/882#issuecomment-20165378 (Yay!) They're asking for someone to help them up with setup scripts. They mention their cookbook collection here: https://github.com/travis-ci/travis-cookbooks In that thread above, I pasted our little script that fetches and installs multiple GHC versions, but I have little experiences with cloud technologies & VMs. Can someone jump in and help push this forward? As a community I'm sure it would be great to get a higher percentage of Hackage packages using simple, hosted continuous testing... I'd personally like to replace my Jenkins install if they can get the necessary GHC versions in there. Best, -Ryan

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Re: [Haskell-cafe] LLVM Backend status
by JP＠eukor.com 28 Jun '13

28 Jun '13

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Job opportunities at Galois
by Iavor Diatchki 28 Jun '13

28 Jun '13

Hello, Galois is hiring! We're looking for researchers, principal investigators, and software engineers, including those with expertise in functional programming, formal methods, computer security, control systems, informatics, or networking. For more information, take a look at http://corp.galois.com/careers and please feel free to drop me an e-mail if you have questions. Cheers, -Iavor

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Re: [Haskell-cafe] LLVM Backend status
by JP＠eukor.com 28 Jun '13

28 Jun '13

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Going to speak about Haskell at Flock to Fedora
by Garrett Mitchener 27 Jun '13

27 Jun '13

(Sorry if you get this twice, I had some trouble with google groups and the mailing list...) Hi, Red Hat is holding a conference called Flock to Fedora<http://flocktofedora.com/> in Charleston, SC, and I'm going to be speaking about Haskell: http://sched.co/14twxPj I'm planning to introduce the language, touch a few interesting packages, and show how to use GHC on Fedora. If anyone from the Haskell community is going to Flock and has requests or suggestions for what I should talk about, post a reply! -- Garrett Mitchener, associate professor of mathematics, College of Charleston, SC

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