Yes, certainly... Otherwise the library would not be much use! If it seems counterintuitive, as it did to me at first, you should check out the "Implicit Configurations" paper, which uses modular arithmetic as an example. My version of their code is in http://ofb.net/~frederik/futility/src/Prepose.hs The function I mainly use is: reifyIntegral :: Integral a => a -> (forall s. ReflectNum s => s -> w) -> w which turns an integral value into a type of the ReflectNum class which represents that value, and calls the provided polymorphic function with a dummy value (actually 'undefined') of that type; then returning the function's result. Frederik On Sat, Apr 15, 2006 at 06:14:44PM +0200, Alberto Ruiz wrote:
On Friday 14 April 2006 17:02, Frederik Eaton wrote:
An index-aware linear algebra library in Haskell
Excellent work!
Is it possible to create a vector or matrix whose size is not known at compile time?
- Due to the need to specify index types at some point, input of vectors is difficult. I have provided two functions in Fu.Vector.Base which should cover most of the cases:
listVec :: Vector v e => [e] -> (forall n . (ReflectNum n) => v (L n) -> w) -> w listMat :: Vector v e => [[e]] -> (forall n m . (ReflectNum n, ReflectNum m) => v (L m, L n) -> w) -> w
However, these aren't useful in interactive situations. So I have also provided some template-haskell routines
http://ofb.net/~frederik/futility/src/Vector/Template.hs
which can be used to instantiate vectors directly. For example:
(In examples.hs):
-- matrix with elements of type Double v6 = trans $(dAM [[1,2,3,4]])
v7 = $(dAM [[1,0,0],[0,1,0],[0,0,1],[1,1,1]])
-- Alberto