[Haskell-cafe] Extending constraints
Bas van Dijk
v.dijk.bas at gmail.com
Tue Jun 5 18:14:48 CEST 2012
On 5 June 2012 17:57, Bas van Dijk <v.dijk.bas at gmail.com> wrote:
> It works.
It turns out it doesn't work exactly as I want. Say I have this
ProxyWrapper of Nums:
p :: ProxyWrapper Num
p = ProxyWrapper (Proxy :: Proxy Int)
then the following would give a type error:
oops :: TypeRep
oops = typeOfInnerProxy p
Couldn't match expected type `Ext Typeable constraint0'
with actual type `Num'
Expected type: ProxyWrapper (Ext Typeable constraint0)
Actual type: ProxyWrapper Num
In the first argument of `typeOfInnerProxy', namely `p'
In the expression: typeOfInnerProxy p
More information about the Haskell-Cafe