Copyright	(c) James M. Lawrence
License	MIT
Maintainer	James M. Lawrence <llmjjmll@gmail.com>
Stability	provisional
Portability	portable
Safe Haskell	Safe
Language	Haskell2010

Math.CayleyDickson

Contents

Types
Construction
Operations
- Operations with scalars
Accessors
Constants
Classes
- Tags

Description

Cayley-Dickson constructions (complex numbers, quaternions, octonions, sedenions, etc.) over general scalars without limit to the number of dimensions.

An element of this structure is composed of an m-dimensional scalar part and an m*(2^n - 1)-dimensional pure part (unrelated to Haskell's uses of "pure"). An element whose scalar part is zero is called a pure. Construction with real scalars yields the Cayley-Dickson algebras, in which case the scalar part is also called the real part. Other structures may be obtained by considering general scalars, for instance the quaternions over complex scalars.

Synopsis

Types

data Nion n a Source

General Cayley-Dickson construction producing "N-ions". The first parameter is a Tag instance that determines the dimension, which is 2 raised to tagVal. The second parameter is the scalar type.

Instances

(Conjugable a, Eq a) => Eq (Nion n a) Source
(Tag n, Conjugable a, RealFloat a) => Floating (Nion n a) Source	The first pure basis element is arbitrarily chosen as sqrt (-1).
(Conjugable a, Fractional a) => Fractional (Nion n a) Source
Conjugable a => Num (Nion n a) Source
(Tag n, Show a, Num a) => Show (Nion n a) Source
Conjugable a => Conjugable (Nion n a) Source

type Complex a = Nion Tag1 a Source

Complex numbers, the 2^1-dimensional construction.

type Quaternion a = Nion Tag2 a Source

Quaternions, the 2^2-dimensional construction.

type Octonion a = Nion Tag3 a Source

Octonions, the 2^3-dimensional construction.

type Sedenion a = Nion Tag4 a Source

Sedenions, the 2^4-dimensional construction.

Construction

nion :: (Tag n, Num a) => [a] -> Nion n a Source

Construct an element from a list of coordinates. If the list is too small then the remaining coordinates are padded with zeros. If the list is too large then the extra values are ignored.

fromScalar :: a -> Nion n a Source

Promote a scalar, returning an element whose scalar part is the argument and whose pure part is zero. The element behaves as if it were padded with zeros, but no actual padding is done.

complex :: a -> a -> Complex a Source

Construct a complex number.

quaternion :: a -> a -> a -> a -> Quaternion a Source

Construct a quaternion.

octonion :: a -> a -> a -> a -> a -> a -> a -> a -> Octonion a Source

Construct an octonion.

sedenion :: a -> a -> a -> a -> a -> a -> a -> a -> a -> a -> a -> a -> a -> a -> a -> a -> Sedenion a Source

Construct a sedenion.

Operations

dot :: Conjugable a => Nion n a -> Nion n a -> a Source

Dot product. (1 `dot`) is equivalent to scalarPart.

cross :: Conjugable a => Nion n a -> Nion n a -> Nion n a Source

Cross product. (1 `cross`) is equivalent to purePart. The cross product of two pures yields an element that is orthogonal to both operands.

sqnorm :: Conjugable a => Nion n a -> a Source

Squared norm: the dot product of an element with itself.

norm :: (Conjugable a, Floating a) => Nion n a -> a Source

Square root of sqnorm.

polar :: (Tag n, Conjugable a, RealFloat a) => Nion n a -> (a, a, Nion n a) Source

Return (s, t, u) such that (approximately)

x == s .* exp (t .* u)

where s and t are scalars, s >= 0, and u is a unit pure.

If x has no pure part then u is arbitrarily chosen to be the first pure basis element.

Operations with scalars

The mnemonic is that the period (".") is on the side of the scalar.

(**.) :: (Tag n, Conjugable a, RealFloat a) => Nion n a -> a -> Nion n a infixr 8 Source

Raise to a scalar power.

(.+) :: Conjugable a => a -> Nion n a -> Nion n a infix 6 Source

Equivalent to fromScalar x + y.

(+.) :: Conjugable a => Nion n a -> a -> Nion n a infix 6 Source

Equivalent to x + fromScalar y.

(.-) :: Conjugable a => a -> Nion n a -> Nion n a infix 6 Source

Equivalent to fromScalar x - y.

(-.) :: Conjugable a => Nion n a -> a -> Nion n a infix 6 Source

Equivalent to x - fromScalar y.

(.*) :: Conjugable a => a -> Nion n a -> Nion n a infix 7 Source

Equivalent to fromScalar x * y.

(*.) :: Conjugable a => Nion n a -> a -> Nion n a infix 7 Source

Equivalent to x * fromScalar y.

(/.) :: (Conjugable a, Fractional a) => Nion n a -> a -> Nion n a infix 7 Source

Equivalent to x / fromScalar y.

Accessors

coord :: (Tag n, Num a, Integral b, Bits b) => Nion n a -> b -> a Source

Get the nth coordinate.

coords :: (Tag n, Num a) => Nion n a -> [a] Source

List of coordinates for this element.

setCoord :: (Tag n, Conjugable a, Integral b, Bits b) => Nion n a -> b -> a -> Nion n a Source

Set the nth coordinate, returning a new element.

scalarPart :: Nion n a -> a Source

Equivalent to coord x 0.

purePart :: Num a => Nion n a -> Nion n a Source

Equivalent to setCoord x 0 0.

Constants

basisElement :: (Tag n, Conjugable a, Bits i, Integral i) => i -> Nion n a Source

The nth basis element.

Classes

class Num a => Conjugable a where Source

The conjugate of an element is obtained by negating the pure part and conjugating the scalar part. The conjugate of a real number is the identity (id), which is the default implementation.

Minimal complete definition

Nothing

Methods

conj :: a -> a Source

Conjugate.

scalarPart' :: a -> a Source

Equivalent to (x + conj x) / 2.