[Haskell-cafe] The instability of Haskell libraries

[Ivan Lazar Miljenovic]

Roman Leshchinskiy <rl at cse.unsw.edu.au> writes:
> John Goerzen gave one in the very first post of this thread: the fix
> to old-locale which didn't change any types but apparently changed the
> behaviour of a function quite drastically. Another example would be a
> change to the Ord instances for Float and Double which would have
> compare raise an exception on NaNs as discussed in a different thread
> on this list. Another one, which is admittedly silly but demonstrates
> my point, would be changing the implementation of map to
>
> map _ _ = []
>
> In general, any significant tightening/changing of preconditions and
> loosening/changing of postconditions would qualify.

OK, fair enough, I see how these can be considered changing the API.
Thing is, whilst it would be possible in general to have a tool that
determines if the API has changed based upon type signatures, etc. how
would you go about automating the test for detecting if the "intention"
of a function changes in this manner?

-- 
Ivan Lazar Miljenovic
Ivan.Miljenovic at gmail.com
IvanMiljenovic.wordpress.com