Thanks to everyone who replied, indeed it looks like GADTs do what I
claimed I wanted. That's neat because I've never been able to think of
a use for them. However:
On Sun, Sep 15, 2013 at 2:16 AM, o...@okmij.org wrote:
Why not to introduce several type classes, even a type class for each
I've been toying with using Data Types a la Carte to get type
representations, a `Typeable` class and dynamic types parameterized by a
possibly open universe:
If the universe is potentially open, and if we don't care about
exhaustive pattern-matching check (which is one of the principal
2013-09-15 11:16, o...@okmij.org skrev:
Evan Laforge wrote:
I have a typeclass which is instantiated across a closed set of 3
types. It has an ad-hoc set of methods, and I'm not too happy with
them because being a typeclass forces them to all be defined in one
place, breaking modularity. A
On 09/15/2013 09:38 AM, Evan Laforge wrote:
...
It seems to me like I should be able to replace a typeclass with
arbitrary methods with just two, to reify the type and back. This
seems to work when the typeclass dispatches on an argument, but not on
a return value. E.g.:
...
Say m_argument
Evan Laforge wrote:
I have a typeclass which is instantiated across a closed set of 3
types. It has an ad-hoc set of methods, and I'm not too happy with
them because being a typeclass forces them to all be defined in one
place, breaking modularity. A sum type, of course, wouldn't have that
You can indeed use GADTs to solve this:
{-# LANGUAGE GADTs #-}
data Universe a where
UInt :: Int - Universe Int
UChar :: Char - Universe Char
class Universal a where
universe :: a - Universe a
instance Universal Int where
universe = UInt
instance Universal Char where
[I too had the problem sending this e-mail to Haskell list.
I got a reply saying the message awaits moderator approval]
Evan Laforge wrote:
I have a typeclass which is instantiated across a closed set of 3
types. It has an ad-hoc set of methods, and I'm not too happy with
them because being
