[Haskell-cafe] Re: type trickery
oleg at okmij.org
oleg at okmij.org
Thu Dec 20 05:57:35 EST 2007
Adrian Neumann wrote:
> I figured I'd need something like this
> data GF = GF Integer Integer
> so that each element of the finite field would remember p. However I
> can't think of a way to use the typesystem to ensure that p is always
> the same.
You might like:
Vectro: Haskell library for "statically typed linear algebra"
http://ofb.net/~frederik/stla/
which marks each element of a vector space with its dimension. The
type system makes sure that you can only add vectors of the same
dimension (the type system does even more: it computes the dimension
of a result of multiplying a vector by a non-square matrix, for
example).
> I think that would need an infinite number of different types,
You think correctly. Haskell already has the infinite number of different
types (e.g., the infinite number of function types).
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