[Haskell-cafe] Re: Re: Re: Hit a wall with the type system

Dan Piponi dpiponi at gmail.com
Thu Nov 29 19:15:57 EST 2007


> I could change my implementation; I could use Jerzy's
> implementation...launch Mathematica...

But all of these could be implemented by introducing a different type
constructor called AD for each one. You could switch the
implementation of AD on the user and they wouldn't have to change a
line of their code. I've no doubt there's a real problem you're trying
to solve, but I'm trying to figure out what it is. Can you post an
example piece of code that would break if you exposed AD, and which
means you need to hide it? (I fully understand the idea of abstracting
over the algorithm, I'm just trying to pin down exactly why you need
the abstraction, and what breaks if you don't have it.)

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