Re: Desugaring overloaded functions

8 Nov 2006

      Hello,

I have another question about the desugarer.

When I desugar and apply OccurAnal.occurAnalysePgm on:

incL [] = []
incL (x : xs) = (1 + x) : (incL xs)

I get the beautiful:

Test.incL :: forall a_ad8. (GHC.Num.Num a_ad8) => [a_ad8] -> [a_ad8]
 [Exported]
 []
 Test.incL =
   \ (@ a_akG) ($dNum_akS :: {GHC.Num.Num a_akG}) ->
     let {
       $dNum_alc [Once Nothing] :: {GHC.Num.Num a_akG}
       []
       $dNum_alc = $dNum_akS } in
     let {
       fromInteger_al9 [Once! Nothing] :: GHC.Num.Integer -> a_akG
       []
       fromInteger_al9 = GHC.Num.fromInteger @ a_akG $dNum_alc } in
     let {
       $dNum_al7 [Once Nothing] :: {GHC.Num.Num a_akG}
       []
       $dNum_al7 = $dNum_akS } in
     let {
       +_akN [OnceL! Nothing] :: a_akG -> a_akG -> a_akG
       []
       +_akN = GHC.Num.+ @ a_akG $dNum_al7 } in
     let {
       lit_akM [OnceL Nothing] :: a_akG
       []
       lit_akM = fromInteger_al9 (GHC.Num.S# 1) } in
     __letrec {
       incL_akO [OnceL! Nothing] :: [a_akG] -> [a_akG]
       []
       incL_akO = incL_akH;
       incL_akH [LoopBreaker Nothing] :: [a_akG] -> [a_akG]
       []
       incL_akH =
         \ (ds_dle [Once! Nothing] :: [a_akG]) ->
           case ds_dle of wild_B1 [Dead Nothing] {
             [] -> GHC.Base.[] @ a_akG;
             : x_adb [Once Nothing] xs_adc [Once Nothing] ->
               GHC.Base.: @ a_akG (+_akN lit_akM x_adb) (incL_akO xs_adc)
           };
     } in  incL_akH

This is almost exactly what I want. There is one thing I don't understand 
though. Namely the __letrec defining:

incL_akO = incL_akH
incL_akH = ... incL_ak0 ...

Why this indirection? Is this also because the desugarer tries to do the most 
simple thing? Or is there an other reason?

And is there a preprocess function that translates this into:

incL_akH = ... incL_akH ... ?

regards,

Bas van Dijk