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 :: {
On 18 May 2013 11:16, TP wrote:
>
> 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 StandaloneDeriving #-}
> {
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
On Sat, May 18, 2013 at 9:11 AM, TP wrote:
>
> So the following version does not work:
>
> [..]
> data Person :: Gender -> * where
> Dead :: Person Gender -- WHAT DO I PUT HERE
> Alive :: { name :: String
> , weight :: Float
>
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 cl
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 l
