Re: [Hs-Generics] Regular problem

Hi Pedro, On 01/17/2011 05:14 PM, José Pedro Magalhães wrote:

This looks like a bug to me, thanks for reporting. I will fix it soon. Great, I'm not very fluent in template haskell... Thanks,

Maarten

Cheers, Pedro

On Mon, Jan 17, 2011 at 17:08, lists@snowlion.nl mailto:lists@snowlion.nl mailto:lists@snowlion.nl> wrote:

Hi all,

/(I think something went wrong with my previous email, so if this is sent twice, I apologize) / Why do self referential structure omit the selector in record entries referencing themselves when converting to the regular data structure?

For instance, when splicing the following data structure:

data P = V {v::String} | II {i::Integer} | P { p::P } deriving Show

$(deriveAll ''P "PFP") type instance PF P = PFP

It generates the following code:

...generics@haskell.org mailto:generics@haskell.org data P_P_ = ... instance Constructor P_P_ where { conName _ = "P" conIsRecord _ = True } ... data P_P_p_ = instance Selector P_V_v_ where { selName _ = "v" } ... instance Selector P_P_p_ where { selName _ = "p" } type PFP = :+: (C P_V_ (S P_V_v_ (K String))) (:+: (C P_II_ (S P_II_i_ (K Integer))) (C P_P_ I)) instance Regular P where { ...generics@haskell.org mailto:generics@haskell.org from II f0 = R (L (C (S (K f0)))) from P f0 = R (R (C (I f0))) ... to R L C S K f0 = II f0 to R R C I f0 = P f0 }

Why is the selector name in case of a self referencing record omitted? I would have expected something like this:

type PFP = :+: (C P_V_ (S P_V_v_ (K String))) (:+: (C P_II_ (S P_II_i_ (K Integer))) (C P_P_ (S P_P_p_ I)))

and likewise:

from II f0 = R (L (C (S (K f0)))) from P f0 = R (R (C (S (I f0)))) ... to R L C S K f0 = II f0 to R R C S I f0 = P f0 }

This gives problems when parsing these kind of structure, or am I missing something?

kind regards,

Maarten

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