October 2003 - template-haskell

RE: [Template-haskell] TH bug report (again)
by Simon Peyton-Jones 30 Oct '03

30 Oct '03

Thanks for the report; now fixed in the HEAD. Simon | -----Original Message----- | From: template-haskell-bounces(a)haskell.org [mailto:template-haskell-bounces@haskell.org] On | Behalf Of Sean Seefried | Sent: 16 October 2003 13:02 | To: template-haskell(a)haskell.org | Subject: [Template-haskell] TH bug report (again) | | Hi again, | | ----------- | d_show = [d| data A = A | | instance Show A where | show _ = "A" | |] | | -------------- | gives | | ---------------------- | ghc-6.2: panic! (the `impossible' happened, GHC version 6.2): | Failed binder lookup: GHCziShow.show {- v rKy -} | | Please report it as a compiler bug to glasgow-haskell-bugs(a)haskell.org, | or http://sourceforge.net/projects/ghc/. | ----------------------- | This might not be a bug, but if it's not can you please tell me what I | am doing wrong? | | Sean | | _______________________________________________ | template-haskell mailing list | template-haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/template-haskell

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RE: [Template-haskell] RE: Template Haskell...
by Simon Peyton-Jones 30 Oct '03

30 Oct '03

Our plan for error messages was failWith :: String -> Q () Would that do? In this way you can format your own error message. So if you had f :: Int -> Q Exp f 0 = failWith "Postitive n required f n = [| \x -> x+n |] then the splice ....$(f 0)..... would elicit the error message Foo.hs:8: Error in splice $(f 0): Positive n required Is that what you want? Simon | -----Original Message----- | From: Alastair Reid [mailto:alastair@reid-consulting-uk.ltd.uk] | Sent: 29 October 2003 21:47 | To: Simon Peyton-Jones; template-haskell(a)haskell.org | Subject: Re: [Template-haskell] RE: Template Haskell... | | More things for the TH wish-list: | | I've been using TH to create language extensions. | Unfortunately, the error messages are horrible because: | | 1) They contain a header generated by TH. | This contains useful information like line numbers but it | talks about TH instead of talking about my extension. | | I want to be able to format the error message header myself using | information like filename and line number that TH provides to me. | | 2) They contain a body generated by TH. | If the code my language extension generates is wrong, | there's virtually no chance that any user (myself included) | will figure it out from seeing the machine-generated Haskell | code or being given the type error message. | Better just to say there is a problem and leave it at that. | | I want to be able to construct the error message body myself | using information like the expression being spliced before | evaluation, after evaluation and the error message produced. | | | A related issue is that I generate files corresponding to each TH module I | compile. If ghc is producing a file called foo/bar.o, I'd like the name of | the file to be foo/bar_stub.o. For this sort of application, I need access | to the name of the input and output filenames. | | Finally, can you drop the 'tick' from variable names produced using gensym? | If you'd used underscore, the variable name would be a legal C identifier | too. (Ok, so this is a bit specialized but it's very easy to do.) | | -- | Alastair Reid www.haskell-consulting.com |

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TH bug report (again)
by Sean Seefried 16 Oct '03

16 Oct '03

Hi again, ----------- d_show = [d| data A = A instance Show A where show _ = "A" |] -------------- gives ---------------------- ghc-6.2: panic! (the `impossible' happened, GHC version 6.2): Failed binder lookup: GHCziShow.show {- v rKy -} Please report it as a compiler bug to glasgow-haskell-bugs(a)haskell.org, or http://sourceforge.net/projects/ghc/. ----------------------- This might not be a bug, but if it's not can you please tell me what I am doing wrong? Sean

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TH bug report
by Sean Seefried 16 Oct '03

16 Oct '03

Dear Template Haskell users, I just wrote a short program with this declaration and got the following error message. ----- d_class = [d| class Classy a b where f :: a -> b instance Classy Int Bool where f x = if x == 0 then True else False |] ------ Class `Test.Classy' does not have a method `f' In the instance declaration for `Test.Classy Int Bool' In the definition of `d_class': d_class = [d| class Test.Classy a b where { Test.f :: a -> b {- has default method -}; } instance {Test.Classy Int Bool} where [] f x y = if x == 0 then True else False |] ------ This doesn't seem like correct behaviour to me. Sean

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Pre-Call for Contributions -- HC&A Report (November 2003 edition)
by C.Reinke 02 Oct '03

02 Oct '03

[apologies for multiple copies - experience has shown that not all Haskellers can be reached via the main Haskell list anymore] An entry for your diaries (no other action required right now): ------------------------------Pre-Call-------------------------------- Your contributions to the November 2003 edition of the Haskell Communities & Activities Report will be invited soon. http://www.haskell.org/communities/ Submissions are welcome between 20th and 31st of October ---------------------------------------------------------------------- The real Call for Contributions will follow closer to the submission window, in about two weeks. This is just an early warning. You will need to plan about 15 minutes for composing your contribution, which would be a brief, ASCII-format, description of your Haskell activities (see earlier editions for plenty of examples). Cheers, Claus (current editor of HC&A Reports)

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