Re: Arrows for invertible programming: Notation, question

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Re: Arrows for invertible programming: Notation, question

Arjen van Weelden
On Fri, 23 Dec 2005, Joel Reymont wrote:

 > Folks,
 >
 > I have been looking at the code for the "Arrows for invertible
 > programming" paper (http://www.cs.ru.nl/A.vanWeelden/bi-arrows/) and
 > I have a question about syntax. ghci surely does not like it.
 >
I've updated the web page to say that is does not work with Hugs, GHCi
or GHC -fgenerics, sorry for the confusion.
It really requires Generic Haskell (GH) 1.42. I never got GH working
with GHC 6.4, so you also really need GHC 6.2.2. I think you can run the
result of the GH preprocessor (using the right command line options) in
GHCi or Hugs, but I'm not sure.

If anyone got GH working with GHC 6.4(+), please tell me how you did it.

 > What does this mean and how do I make it compile?
 >
 > mapl{|a, b|arr|} :: (mapl{|a, b|arr|}, ArrowChoice arr, BiArrow arr)
 > => arr a b
 >
In GH this means: mapl is a polytypic (type-indexed in a and b) function
that yields an arr(ow) from a to b. It is overloaded in ArrowChoice and
BiArrow on the arr(ow). Because it is polytypic, it is also overloaded
`in itself'. Most of the time GH does not require the last part
explicitly, but sometimes it triggers a bug if you don't specify it.
The semantics of mapl can be found in the paper.

regards,
        Arjen

 >       Thanks, Joel
 >
 > --
 > http://wagerlabs.com/
 >
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Re: Arrows for invertible programming: Notation, question

Alexey Rodriguez Yakushev-2

On Dec 23, 2005, at 11:53, Arjen wrote:

> On Fri, 23 Dec 2005, Joel Reymont wrote:
>
> > Folks,
> >
> > I have been looking at the code for the "Arrows for invertible
> > programming" paper (http://www.cs.ru.nl/A.vanWeelden/bi-arrows/) and
> > I have a question about syntax. ghci surely does not like it.
> >
> I've updated the web page to say that is does not work with Hugs, GHCi
> or GHC -fgenerics, sorry for the confusion.
> It really requires Generic Haskell (GH) 1.42. I never got GH working
> with GHC 6.4, so you also really need GHC 6.2.2. I think you can run
> the result of the GH preprocessor (using the right command line
> options) in GHCi or Hugs, but I'm not sure.

Once you have compiled your GH program (.ghs) into a haskell program
(.hs), you can load it into ghci using the wrapper provided in
build/bin/gh-ghci .

>
> If anyone got GH working with GHC 6.4(+), please tell me how you did
> it.

To build GH with the 6.4 series of GHC you need to check out the
sources from the subversion repository:

svn co
https://svn.cs.uu.nl:12443/repos/Generic-Haskell/trunk/Generic-Haskell/


Cheers,

Alexey

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