Re: ghc search paths (like CPATH for gcc)

[Misha Aizatulin]

Simon Marlow wrote:
 On 19/10/2009 05:17, Misha Aizatulin wrote:
 Hello,

is there a mechanism for ghc similar to setting the CPATH variable for
 gcc? I'd like ghc to look in the given list of paths every time it
 compiles something, without me having to retype the flags.

For ghci there is .ghci, but it gets ignored when I run ghc.
 
 We don't have anything like that right now.  Please submit a feature
 request:

  Done:
http://hackage.haskell.org/trac/ghc/ticket/3619

Misha

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ghc search paths (like CPATH for gcc)

[Misha Aizatulin]

Hello,

  is there a mechanism for ghc similar to setting the CPATH variable for
gcc? I'd like ghc to look in the given list of paths every time it
compiles something, without me having to retype the flags.

  For ghci there is .ghci, but it gets ignored when I run ghc.

Best,
  Misha
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Dumping context reduction steps

[Misha Aizatulin]

hi,

  is there some command line switch in GHC that would allow me to see
context reduction steps during the compilation?

Thanks,
  Misha

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Re: [Haskell] Deferred instance declarations (serialization of existential boxes)

[Misha Aizatulin]

Simon Peyton-Jones wrote:
 Concerning your application

 |   I am having a box like
 |  data Box = forall a. Cxt a = Box a
 |   and want to write a Read instances for it.

 I don’t see how it helps to defer the Read instance.

  I would defer the instance declaration till the point where I know all
types that will ever go into the box (for instance in my Main module).
The Show instance of Box would write the representation of a together
with it's type (this means Cxt should contain at least Show and
Typeable). The Read instance will then contain something like


  String aType- lexP

  result - case aType of
[Int] -
  (readPrec :: ReadPrec [Int]) = (return . Box)
SomeOtherType -
  (readPrec :: ReadPrec SomeOtherType) = (return . Box)

-- more of such cases

_ - error (aType ++  cannot be read inside of Box)
 

  Not very elegant of course, but it seems to be the only way to Read
existentials.

 But I think the case is stronger for top-level constraints, and I will bear 
 it in mind.  
 If you would like to open a Trac feature request, please do so.

  Ok, I will.

Cheers,
  Misha
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