[Haskell] Eternal Compatibility In Theory

[Keean Schupke]

robert dockins wrote:

>>> Is there a way to reliably and automatically check if two versions of
>>> a haskell module are interface compatible?
>>
>>  
>> No, because it would have to check whether the semantics of functions
>> is the same, even if they are written differently.
>
>
> Of course, we cannot expect the computer to examine the semantics.  We
> must rely on people to know when semantics change.
>
> Suppose I want to ask the easier question "do these two text files
> implement haskell modules which are _type_ compatable?", how would I
> do it?  Ie, I want the test to fail if I change the type of some
> function foo, or if I add a method to a class declaration etc.
>
>
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Is this true? Can't you use an IDL to specify the interface more
exactly. I would have thought a definition of the protocol was enough.

If you define a protocol definition language then it should be possible
to check both ends of the connection to see if the conform to the protocol.

    Keean.