Hi Cafe, I've created a numpy equivalent for Haskell. (Numpy is a python library for multi-dimensional arrays and operations on them) Code at http://github.com/yairchu/numkell (not yet on hackage because it needs better names) A numkell array is a pair of a function from integer inputs and a range for its inputs (size). This allows for easy memoizing into in-memory arrays, and additionally, numkell arrays also support useful operations like numpy's newaxis and folding axes away. As the "Array" name was already taken, numkell's array is currently called "Funk" (name suggestions very appreciated). An example: Given an bunch of vectors as a 2d array, compute the distance between each pair of vectors {-# LANGUAGE DeriveDataTypeable, GeneralizedNewtypeDeriving, TypeOperators #-} import Data.HList import Data.NumKell import Data.Typeable newtype PersonIdx = PersonIdx Int deriving (Enum, Eq, Integral, Num, Ord, Real, Show, Typeable) newtype FeatureIdx = FeatureIdx Int deriving (Enum, Eq, Integral, Num, Ord, Real, Show, Typeable) let personProps = fFromList [[5,3,2],[4,8,1],[2,6,9],[5,3,0]] :: Funk (HJust PersonIdx :*: HJust FeatureIdx :*: HNil) Double
personProps FeatureIdx 0 1 2 PersonIdx + - - - 0 | 5.0 3.0 2.0 1 | 4.0 8.0 1.0 2 | 2.0 6.0 9.0 3 | 5.0 3.0 0.0
sumAxes (fmap (** 2) (liftF2 (-) (personProps !/ (SNewAxis .*. HNil)) (personProps !/ (SAll .*. SNewAxis .*. HNil)))) (TFalse .*. TFalse .*. TTrue .*. HNil)
PersonIdx 0 1 2 3 PersonIdx + - - - - 0 | 0.0 27.0 67.0 4.0 1 | 27.0 0.0 72.0 27.0 2 | 67.0 72.0 0.0 99.0 3 | 4.0 27.0 99.0 0.0 In Python the last line looks shorter:
((personProps[newaxis] - personProps[:,newAxis]) ** 2).sum(2)
Mostly due to Python's slicing syntax sugar. Still, numkell has one large benefit over numpy (apart from being for Haskell): With numpy this example creates a temporary 3d array in memory. In numkell the array is not allocated in memory unless "fMemo" is called. If anyone has comments, suggestions, naming suggestions, complaints, etc, I would very much like to hear. cheers, Yair