Re: deriving...

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 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

_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users