Actually, IIRC, _|_ is actually a member of _all_ types.
--ag
"S. Alexander Jacobson" wrote:
>
> On Tue, 28 Sep 1999, Adrian Hey wrote:
>
> > So (a && b) = (b && a) is invalid
>
> && has type
> &&::Boolean->Boolean->Boolean
>
> _|_ is not of type Boolean. So, if you pass && a value of type
>Can some one please fill me in on why existential types are not
> part of Haskell 98? Probably this is answered in some paper/statement
> that I can read some where? I sort of understand them (* I am still
> learning haskell. WOrking through S.T's book right now *) but
> not enough perhaps
Though I am _not_ exactly a Haskell expert, I could not avoid
commenting...
Kevin Atkinson wrote:
>
> Here is a laundry list of things I think Haskell still needs. By
> Haskell here I mean Haskell plus extension that are found in both hugs
> and ghc.
>
> 1) Support for true ad-hoc overloading.
>
> I am trying to write some primitives to make it easy to manipulate haskell
> datatypes without knowing what they are.
>
> However the following class:
>
> > class MetaData a where
> > constructorName::a->String
> > mapArgs::(MetaData b,MonadPlus c) => (b->c)->a->[c]
>
> results in the er
Why not Haskell I?
(as the first "standard" form of the language)...
--Artie
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>---
Arthur Gold Austin, Texas
** [EMAIL PROTECTED] [EMAIL PROTECTED] **
"`Go to' considered harmful" -- E. Dijkstra
"Go to, go to!" -- W. Shakespeare (Hamlet Act I. Sc. III L. 118)
make a
function call, etc.; laziness enables the encapsulation of functionality
within functions--even though the actual control flow is often much more
complex.
As a result, purely functional, lazy data structures can be a little tough
to get one's head around.
--Artie
Arthur Gold
ense to
me intuitively).
Was this a conscious design decision?
...and if so, why?
Thanks.
--Artie
Arthur Gold Austin, Texas
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