Hal Daume wrote:
> -- *Main> test $ MkFoo (0::Int)
> -- Just True
> -- *Main> test $ MkBar 'a'
> -- Just True
> i forgot to mention the constraint
> that i don't want the user to have to use the MkFoo/MkBar
> constructors. if i could use them internally to 'test', that would be
> great, bu
#x27;cast' function in Section 3 of "Scrap your
> boilerplate" useful.
> http://research.microsoft.com/~simonpj/papers/hmap/
> I'm not certain, but it has the right smell.
> Simon
>
> | -Original Message-
> | From: [EMAIL PROTECTED] [mailto:[EMAIL PRO
| Sent: 21 March 2003 04:19
| To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
| Subject: Re: simulating dynamic dispatch
|
|
| > i'm hoping to be able to simulate a sort of dynamic dispatch based
on
| > class instances.
|
| It seems you want to dispatch based not on a type but on the
|
On 20-Mar-2003, Hal Daume III <[EMAIL PROTECTED]> wrote:
> i'm hoping to be able to simulate a sort of dynamic dispatch based on
> class instances. basically a function which takes a value and depending
> on what classes it is an instance of, does something.
I call this feature "dynamic type clas
> -- *Main> test $ MkFoo (0::Int)
> -- Just True
> -- *Main> test $ MkFoo (10::Int)
> -- Just False
> -- *Main> test $ MkBar 'a'
> -- Just True
> -- *Main> test $ MkBar 'b'
> -- Just False
ah, yes. i was aware that would work. i forgot to mention the constraint
that i don't want the user t
> i'm hoping to be able to simulate a sort of dynamic dispatch based on
> class instances.
It seems you want to dispatch based not on a type but on the
constraint of a type.
You code almost worked. Here's the a bit updated and working version.
class Foo a where { foo :: a -> Bool }
class Bar a
