[Hs-Generics] Regular problem

[José Pedro Magalhães]

Hi Maarten,

This looks like a bug to me, thanks for reporting. I will fix it soon.


Cheers,
Pedro

On Mon, Jan 17, 2011 at 17:08, lists at snowlion.nl <lists at 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 at 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 at 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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