[Haskell-cafe] Re: haskell compiler never comes back

[Daniel Fischer]

Am Montag, 15. Dezember 2008 23:16 schrieb Greg Meredith:
> Haskellians,
>
> An even simpler version <http://paste.pocoo.org/show/95518/> that reveals
> the issue. i'm astounded that the compiler literally just hangs.
>
> Best wishes,
>
> --greg
>
> On Mon, Dec 15, 2008 at 12:23 PM, Greg Meredith <
>
> lgreg.meredith at biosimilarity.com> wrote:
> > Haskellians,
> >
> > The simple-minded and smallish code sample at this
> > link<http://paste.pocoo.org/show/95503/>causes the compiler to go off
> > into never-never land. Any clues would be greatly appreciated.
> >
> > Best wishes,
> >
> > --greg

I can't confirm it, with 6.8.3:

$ ghc -O2 --make Monoidal.hs
[1 of 1] Compiling Monoidal         ( Monoidal.hs, Monoidal.o )

Monoidal.hs:110:11:
    Couldn't match expected type `i1'
           against inferred type `Isomorpism (HFTensorExpr a i) a'
      `i1' is a rigid type variable bound by
           the instance declaration at Monoidal.hs:103:42
    In the expression: (PutIn (\ a -> (HFTLVal a)))
    In the third argument of `HFTExpr', namely
        `[(PutIn (\ a -> (HFTLVal a)))]'
    In the expression:
        (HFTExpr
           (HFTLVal a)
           (HFTRVal b)
           [(PutIn (\ a -> (HFTLVal a)))]
           [(PutIn (\ b -> (HFTRVal b)))])
$

and the earlier version:

$ ghc -O2 --make Monoidal2.hs
[1 of 1] Compiling Monoidal2        ( Monoidal2.hs, Monoidal2.o )

Monoidal2.hs:105:18:
    Couldn't match expected type `HFTensorExpr a i'
           against inferred type `[i1] -> [i1] -> HFTensorExpr a i1'
    In the expression: HFTExpr (HFTLVal a) (HFTRVal b)
    In the definition of `tMult':
        a tMult b = HFTExpr (HFTLVal a) (HFTRVal b)
    In the definition for method `tMult'

Monoidal2.hs:122:10:
    Couldn't match expected type `[]' against inferred type `++ msa'
      Expected type: [i]
      Inferred type: ++ msa msb
    In the third argument of `HFTExpr', namely
        `((Shuffle
             (\ (HFTExpr (HFTExpr u v msu msv) w msuv msw)
                  -> (tAssoc (HFTExpr (HFTExpr u v msu msv) w msuv msw)))) ::
            msa ++ msb)'
    In the expression:
        (HFTExpr
           (HFTExpr a b msa msb)
           c
           ((Shuffle
               (\ (HFTExpr (HFTExpr u v msu msv) w msuv msw)
                    -> (tAssoc (HFTExpr (HFTExpr u v msu msv) w msuv msw)))) 
::
              msa ++ msb)
           msc)

Monoidal2.hs:139:10:
    Couldn't match expected type `[]' against inferred type `++ msl'
      Expected type: [i]
      Inferred type: ++ msl msr
    In the third argument of `HFTExpr', namely
        `((Shuffle
             (\ (HFTExpr (HFTExpr a b msa msb) c msab msc)
                  -> (tAssoc (HFTExpr (HFTExpr a b msa msb) c msab msc)))) ::
            msl ++ msr)'
    In the expression:
        (HFTExpr
           (HFTExpr l r msl msr)
           (HFTRVal b)
           ((Shuffle
               (\ (HFTExpr (HFTExpr a b msa msb) c msab msc)
                    -> (tAssoc (HFTExpr (HFTExpr a b msa msb) c msab msc)))) 
::
              msl ++ msr)
           [(PutIn (\ b -> (HFTRVal b)))])

Monoidal2.hs:150:11:
    Couldn't match expected type `i1'
           against inferred type `Isomorpism (HFTensorExpr a i) a'
      `i1' is a rigid type variable bound by
           the instance declaration at Monoidal2.hs:103:42
    In the expression: (PutIn (\ a -> (HFTRVal a)))
    In the third argument of `HFTExpr', namely
        `[(PutIn (\ a -> (HFTRVal a)))]'
    In the expression:
        (HFTExpr
           (HFTLVal a)
           (HFTRVal b)
           [(PutIn (\ a -> (HFTRVal a)))]
           [(PutIn (\ b -> (HFTRVal b)))])
$

No hang, which compiler version did you use?