Vec-0.9.8: Fixed-length lists and low-dimensional linear algebra.



Packed vectors : use these whenever possible. The polymorphic vector type is represented at run-time by a linked list of boxed values. Specialized, or packed types, store the vector components sequentially in memory, in a single boxed value. Definitions for vector operations, given in terms of polymorphic vectors, can be (almost) automatically propagated to packed types using the functions pack and unpack. The compiler can then specialize the definition to the packed type and produce efficient code.

Packed vectors are related to their unpacked representations by way of an associated type. An instance of class PackedVec v declares that v has a packed representation, and the type of that is Packed v. The packed constructors are named VecNT where N is 2, 3 or 4 and T is I, F or D for Int, Float or Double. So the expression Vec3D x y z constructs a packed 3-vector of Doubles, the type of which is Packed (Vec3 Double). The constructor name is also a synonym for the packed type name, i.e., type Vec3D = Packed (Vec3 Double), so the packed type acts as if it had been declared data Vec3D = Vec3D x y z.

Storable, Num, Fractional, Fold, Map, and ZipWith instances are provided for packed vectors, so some operations do not require pack/unpack. For example, dot does not require pack/unpack because it is defined in terms of zipWith and fold. However transpose, det, gaussElim and most others are recursive (i.e., defined in terms of the same operation on lower-dimensional vectors), and so you'll still need to use pack/unpack with these. This goes for multmm as well because it uses transpose. Some functions, like multmv, do not need their arguments to be unpacked, but the result is a polymorphic vector (:.), so you will need to pack it again. I admit that this is awkward, and I'm still looking for a better way.

There are also instances for Access, Take, Drop, Last, Head, Tail and Snoc. These come in handy for things like quaternions and homogenous coordinates.



class PackedVec v whereSource

PackedVec class : relates a vector type to its space-optimized representation.

Associated Types

data Packed v Source

The packed representation of v


pack :: v -> Packed vSource

unpack :: Packed v -> vSource

packMat :: (Map row (Packed row) mat packedMat, PackedVec row) => mat -> packedMatSource

Construct a semi-packed matrix, one whose rows are packed.

unpackMat :: (Map (Packed row) row packedMat mat, PackedVec row) => packedMat -> matSource