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"Philip K.F. =?iso-8859-1?q?H=F6lzenspies=22?= | 2 Dec 13:54
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Alex requirement for Setup.lhs

Dear all,

Hopefully, you will excuse me for my lack of experience with Cabal. I have 
seen quite a few e-mails on this list that seem related to this issue, but my 
specific error, I did not find. Thus:

Since installing 6.10.1, I can't perform Setup.(l)hs functions. The error 
message I get is:

Setup.hs: alex is required but it could not be found.

The problem is that I get this error also when I try to "runghc Setup.lhs 
build" alex (is the fact that "runghc Setup.lhs configure" does *not* produce 
this error significant?). I'm running an OpenSuSE 10.3 installation on which 
I can only install rpms from standard repositories. In these repositories, 
there is no binary distribution of alex. How do I install alex from source 
without requiring alex?

Regards,
Philip
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Ian Lynagh | 4 Dec 00:11
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Re: Alex requirement for Setup.lhs

On Tue, Dec 02, 2008 at 01:56:03PM +0100, Philip K.F. Hölzenspies wrote:
> 
> Setup.hs: alex is required but it could not be found.
> 
> The problem is that I get this error also when I try to "runghc Setup.lhs 
> build" alex

If you have downloaded the source tarball then the preprocessed files
are included. Cabal may be getting confused by the .x files also being
present, so
    rm src/Scan.x
should fix it. You may also need to
    rm src/Parser.y
if you don't have happy.

Thanks
Ian
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"Philip K.F. =?iso-8859-1?q?H=F6lzenspies=22?= | 4 Dec 14:24
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Alex compilation fails on ambiguous type [was: Re: Alex requirement for Setup.lhs]

On Thursday 04 December 2008 00:11:13 Ian Lynagh wrote:
> If you have downloaded the source tarball then the preprocessed files
> are included. Cabal may be getting confused by the .x files also being
> present, so
>     rm src/Scan.x
> should fix it. You may also need to
>     rm src/Parser.y
> if you don't have happy.

Dear Ian, all,

Thank you for your tip, Ian. Deleting src/Scan.x did do the trick. However, I 
get a very strange type error when I try to compile alex 2.2. Maybe someone 
knows what's going on here:

[16 of 16] Compiling Main             ( src/Main.hs, 
dist/build/alex/alex-tmp/Main.o )

src/Main.hs:316:25:
    Ambiguous type variable `e' in the constraint:
      `GHC.Exception.Exception e'
        arising from a use of `throw' at src/Main.hs:316:25-31
    Probable fix: add a type signature that fixes these type variable(s)

Lines 314 through 316 in src/Main.hs are:

    r <- Exception.catch 
	   (unblock (thing a))
	   (\e -> do { after a; throw e })
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"Philip K.F. =?iso-8859-1?q?H=F6lzenspies=22?= | 4 Dec 14:39
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Re: Alex compilation fails on ambiguous type [was: Re: Alex requirement for Setup.lhs]

On Thursday 04 December 2008 14:24:32 Philip K.F. Hölzenspies wrote:
> [16 of 16] Compiling Main             ( src/Main.hs,
> dist/build/alex/alex-tmp/Main.o )
>
> src/Main.hs:316:25:
>     Ambiguous type variable `e' in the constraint:
>       `GHC.Exception.Exception e'
>         arising from a use of `throw' at src/Main.hs:316:25-31
>     Probable fix: add a type signature that fixes these type variable(s)
>
> Lines 314 through 316 in src/Main.hs are:
>
>     r <- Exception.catch
> 	   (unblock (thing a))
> 	   (\e -> do { after a; throw e })
>
> I guess the error in itself makes some sense, because throw can not be
> resolved without knowing a concrete instance of e. I just don't get why I
> get this error in a release version of alex; I would imagine other people
> do not get this error. What am I missing?

Dear Ian, all,

Please ignore my previous e-mail. It must have been a remainder from an 
earlier failed build attempt. I just did a checkout from the alex darcs 
repository, which built without a hitch.

Regards,
Philip
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