OOP

[Arthur Gold]

"Robert A. Abernathy" <raa@hybrithms.com> wrote:

>I have a request.  If any of the proposed object oriented
>extensions to Clean are put in place, could the name be changed
>from Clean to Muddy.
>
>Hybrid OOP languages are ugly beasts.  A Clean like OOP
>language could well be a neat thing, but I think it would
>be better to start with the Clean intermediate language
>and build a new pure OO-functional language on top of this
>base.
>
>Rob

You have a point. Attempting to add 'purely-OO' (in the sense of CLOS or
Smalltalk) to a staticly-typed language like Clean, would certainly
'muddy-up' the waters. There's another option, however, that would give the
desired effect: i.e. the addition of typeclass-restricted dynamic types.

Consider the following proposed syntax (roughly along the lines of
existential types)

::ADynamicType = Dyn.a: SomeClass a

which would be roughly equivalent to defining all of the following:

::ADynamicType a = ADynamicType_Type1 a
                 | ADynamicType_Type2 a
                 | ...
                 | ADynamicType_TypeN a


class ToADynamicType a | SomeClass a
where
   toADynamic::a->ADynamicType a

toADynamic::Type1->ADynamicType
toADynamic a = ADynamicType_Type1 a

...

toADynamic::TypeN->ADynamicType
toDynamic a = ADynamicType_TypeN a

instance SomeClass ADynamicType
where
   f1 (ADynamicType_Type1 x) = f1 x
   f1 (ADynamicType_Type2 x) = f1 x
   ...
   f1 (ADynamicType_TypeN x) = f1 x

   f2 (ADynamicType_Type1 x) = f2 x
   ...
   f2 (ADynamicType_TypeN x) = f2 x

   ...

   fN (ADynamicType_Type1 x) = fN x
   ...
   fN (ADynamicType_TypeN x) = fN x

(f1 .. fN are the functions that are members of SomeClass)

Of course, some additional plumbing may be required; in particular, the
results of the various would probably have to be wrapped up in some sort of
dynamic type as well...

Anyway, just a thought.

--Artie







   Arthur Gold                     Austin, Texas
 ** artiegold@weirdness.com  agold@cs.utexas.edu  **

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