Re: deriving...

[Keean Schupke]

Okay so that does the deriving...  How are you deriving the constraints? 
(in the ghc code there is
some equaion expansion, where it finds the fixed point).

Still the main point was that it would be nice to seamlessly integrate 
this... Surely it wouldn't take much
to get the compiler to look for a template-haskell splice $(derivingX)  
when the compiler encounters a "deriving X" statement that is not built-in?

Ulf Norell wrote:
Keean Schupke <[EMAIL PROTECTED]> writes:
   

Yes, I could quite easily write the generator in TemplateHaskell (have
played with it before)
_but_ I don't like the $(xxx) syntax... Perhaps if Simon could be
persuaded to allow deriving
clauses to be defined in TH?
data X x = X x
$(deriveMyClass (reify X))
could perhaps be defined from
data X x = X x deriving MyClass
I saw the same suggestion earlier today on the Haskell list...
     

Check out Ulf Norell's IOHCC submission, his DeriveData.hs module does
this,
though I can't tell if it will work for parameterized types.
   

It doesn't. A version that does can be downloaded from
http://www.cs.chalmers.se/~ulfn/th/DeriveData.hs
/ Ulf
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