Re: [Haskell-cafe] The instability of Haskell libraries

On 24/04/2010, at 18:54, Ivan Lazar Miljenovic wrote:

Roman Leshchinskiy writes:

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On 24/04/2010, at 18:06, Ivan Lazar Miljenovic wrote:

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I would think that the API is all the functions/classes/datatypes/instances/etc. exported from the library in combination with their types.

So the semantics of those functions doesn't matter at all?

What do you refer to by "semantics"? Can you provide an example of when what you consider to be the API to change when the functions, types, etc. don't?

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. Roman