License	MIT
Maintainer	douglas.mcclean@gmail.com
Stability	experimental
Safe Haskell	Safe
Language	Haskell2010
Extensions	RankNTypes ExplicitForAll

Data.ExactPi

Description

This type is sufficient to exactly express the closure of Q ∪ {π} under multiplication and division. As a result it is useful for representing conversion factors between physical units. Approximate values are included both to close the remainder of the arithmetic operations in the Num typeclass and to encode conversion factors defined experimentally.

Synopsis

Documentation

data ExactPi Source

Represents an exact or approximate real value. The exactly representable values are rational multiples of an integer power of pi.

Constructors

Exact Integer Rational	`Exact z q` = q * pi^z. Note that this means there are many representations of zero.
Approximate (forall a. Floating a => a)	An approximate value. This representation was chosen because it allows conversion to floating types using their native definition of `pi`.

Instances

Floating ExactPi Source
Fractional ExactPi Source
Num ExactPi Source
Show ExactPi Source
Monoid ExactPi Source	The multiplicative monoid over `Rational`s augmented with multiples of `pi`.

approximateValue :: Floating a => ExactPi -> a Source

Approximates an exact or approximate value, converting it to a Floating type. This uses the value of pi supplied by the destination type, to provide the appropriate precision.

isZero :: ExactPi -> Bool Source

Identifies whether an ExactPi is an exact or approximate representation of zero.

isExact :: ExactPi -> Bool Source

Identifies whether an ExactPi is an exact value.

isExactZero :: ExactPi -> Bool Source

Identifies whether an ExactPi is an exact representation of zero.

isExactOne :: ExactPi -> Bool Source

Identifies whether an ExactPi is an exact representation of one.

areExactlyEqual :: ExactPi -> ExactPi -> Bool Source

Identifies whether two ExactPi values are exactly equal.

isExactInteger :: ExactPi -> Bool Source

Identifies whether an ExactPi is an exact representation of an integer.

toExactInteger :: ExactPi -> Maybe Integer Source

Converts an ExactPi to an exact Integer or Nothing.

isExactRational :: ExactPi -> Bool Source

Identifies whether an ExactPi is an exact representation of a rational.

toExactRational :: ExactPi -> Maybe Rational Source

Converts an ExactPi to an exact Rational or Nothing.

rationalApproximations :: ExactPi -> [Rational] Source

Converts an ExactPi to a list of increasingly accurate rational approximations, on alternating sides of the actual value. Note that Approximate values are converted using the Real instance for Double into a singleton list. Note that exact rationals are also converted into a singleton list.

Implementation based on work by Anders Kaseorg shared at http://qr.ae/RbXl8M.