[Haskell-cafe] Deriving class instances using DrIFT

John Meacham john at repetae.net
Sun Oct 29 22:56:11 EST 2006

On Mon, Oct 30, 2006 at 01:24:58PM +1300, Daniel McAllansmith wrote:
> I'm trying to derive some instances using DrIFT, but it will only work for me 
> when I'm deriving for types in the current file or in the prelude.

Since DrIFT can only understand haskell source code, it can't derive
instances for anything you don't have the original source to. such as
things in the pre-compiled libraries that come with ghc. you will likely
have to write out those instances by hand. 

Another possibility is that you could replicate just the data
declarations by hand, and use DrIFT -r to just spit out the derivations
and put those in a file on their own.

a long time ago DrIFT used to be able to read ghc 'hi' files, but that
has not worked in a while, it is possible not all the documentation has
been updated to reflect that.


John Meacham - ⑆repetae.net⑆john⑈

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