On 2004-04-28T15:12:03-0400, S. Alexander Jacobson wrote:
Ok, but it sounds like you need to know the list
of possible types in advance. Is it possible
to have a lib take a filepath and type name as an
arbitrary string, and read the instance in?
I don't think you need to know the list of
On 2004-04-28T23:33:31-0400, S. Alexander Jacobson wrote:
I don't think this works. I just tried it with:
main = print $ lookupRead 1 [(1,(Integer,100))]
This fails for the same reason
print $ read 100
fails. You need to give a type signature to avoid type-class instance
ambiguity:
I don't think this works. I just tried it with:
main = print $ lookupRead 1 [(1,(Integer,100))]
How would Haskell know that typ actually does
equal typeOf?
-Alex-
_
S. Alexander Jacobson mailto:[EMAIL
But isn't the point of this code that you don't
need that type signature? If I knew in advance
that it was an Integer then I wouldn't need to
passs Integer in the list.
-Alex-
On Thu, 29 Apr 2004, Chung-chieh Shan wrote:
On 2004-04-28T23:33:31-0400, S. Alexander Jacobson wrote:
I don't
On 2004-04-29T11:50:48-0400, S. Alexander Jacobson wrote:
But isn't the point of this code that you don't
need that type signature? If I knew in advance
that it was an Integer then I wouldn't need to
passs Integer in the list.
In the context in which the code was originally written, the
So let me ask this question a different way. Is
it possible to use Read/Show or Typeable with
Existential types.
Given MyClass and MyType as follows:
class (Read a,Show a,Typeable)=MyClass a where foo::a
type MyType = forall a. MyClass a= [a]
Is there a way to persist MyType?
My
