objective data on use of extensions

[Ian Lynagh]

On Fri, Feb 03, 2006 at 11:38:09AM -0800, Isaac Jones wrote:
> I would like to strive to find objective data on the use of
> extensions.  I started a table here which summarizes how popular
> extensions are in real-life code.  We need more data points, though.
> 
> http://hackage.haskell.org/trac/haskell-prime/wiki/ExtensionsExperiment
> 
> I have a short program which queries the hackage database, gets some
> details about all of the packages there, and summarizes them into a
> table.

I'm not sure how useful this info is, as:

* You won't get, for example, FunctionalDependencies from any libraries
  or applications that make use of Control.Monad.State.

* Many extensions turn into -fglasgow-exts/-98, so if I use
  functional dependencies and rank 2 types but only declare
  FunctionalDependencies and not Rank2Types then nothing is going to
  tell me I've made a mistake. (I think it would be great if this was
  fixed). (Ideally something could warn about unused extensions too, but
  that's trickier).

* People will sometimes be willing to jump through hoops to avoid using
  an unportable extension.


That said, FWIW, I have the following in my cabalised libraries (none in
hackage AFAIK):

* ForeignFunctionInterface, TemplateHaskell, TypeSynonymInstances
* TypeSynonymInstances
* ForeignFunctionInterface
* ForeignFunctionInterface
* EmptyDataDecls, CPP
* EmptyDataDecls, ForeignFunctionInterface

Thanks
Ian