Chris Wong wrote:
data Person :: Gender - * where
Dead :: Person Gender -- WHAT DO I PUT HERE
Alive :: { name :: String
, weight :: Float
, father :: Person Gender } - Person Gender
Here's the problem. In the line:
Dead :: Person Gender
you
On 18 May 2013 11:16, TP paratribulati...@free.fr wrote:
snip
However, I have not managed to make the version with forall work.
Below, the
first occurrence of forall is ok, but the three following yield error.
{-# LANGUAGE GADTs #-}
{-# LANGUAGE
Denis Kasak wrote:
Note that all of this would work even without explicit quantification
since you
have already specified that Person accepts an argument of kind Gender. In
other
words, this works as expected:
data Person :: Gender - * where
Dead :: Person a
Alive :: { name ::
Hi everybody,
I have a question about deriving automatically a Show instance when using
GADT.
It works in this situation:
{-# LANGUAGE GADTs #-}
data Male
data Female
data Person gender where
Dead :: Person gender
Alive :: { name :: String
,
Hi TP,
On 17/05/13 15:32, TP wrote:
| [...]
|
| So I modify my code by removing deriving Show, and adding the line:
|
| instance Show (Person gender)
|
|
| But now, I obtain:
|
| $ runghc test_show.hs
| GHC stack-space overflow: current
Adam Gundry wrote:
[...]
To use standalone deriving, you need to write
deriving instance Show (Person gender)
and everything will work fine. By writing
instance Show (Person gender)
you are instead giving an instance with no methods, and the default
methods in the Show class contain
On Sat, May 18, 2013 at 9:11 AM, TP paratribulati...@free.fr wrote:
So the following version does not work:
[..]
data Person :: Gender - * where
Dead :: Person Gender -- WHAT DO I PUT HERE
Alive :: { name :: String
, weight ::
