[Haskell] Real life examples

Ben Rudiak-Gould Benjamin.Rudiak-Gould at cl.cam.ac.uk
Wed Nov 24 18:18:44 EST 2004

Lennart Augustsson wrote:

 > What do you mean when you say the interface is pure?
 > If your module is really pure then there should be an implemenation
 > of it (which could have really bad complexity) with the same observable
 > behaviour that uses only pure Haskell.  Is this possible?

Really? I agree with the converse of that statement, but I don't think 
it goes both ways. To me a function or module is pure when you can use 
it without compromising the equational properties of the language. I 
don't think Data.Dynamic or Control.Monad.ST satisfy your criterion for 
purity, but I would call them pure (after discarding the functions 
marked unsafe in the latter).

-- Ben

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