Name: numeric-prelude
Version: 0.2
License: GPL
License-File: LICENSE
Author: Dylan Thurston , Henning Thielemann , Mikael Johansson
Maintainer: Henning Thielemann
Homepage: http://www.haskell.org/haskellwiki/Numeric_Prelude
Category: Math
Stability: Experimental
Tested-With: GHC==6.4.1, GHC==6.8.2
Synopsis: An experimental alternative hierarchy of numeric type classes
Description:
Revisiting the Numeric Classes
.
The Prelude for Haskell 98 offers a well-considered set of numeric classes
which covers the standard numeric types
('Integer', 'Int', 'Rational', 'Float', 'Double', 'Complex') quite well.
But they offer limited extensibility and have a few other flaws.
In this proposal we will revisit these classes, addressing the following concerns:
.
[1] The current Prelude defines no semantics for the fundamental operations.
For instance, presumably addition should be associative
(or come as close as feasible),
but this is not mentioned anywhere.
.
[2] There are some superfluous superclasses.
For instance, 'Eq' and 'Show' are superclasses of 'Num'.
Consider the data type
@ data IntegerFunction a = IF (a -> Integer) @
One can reasonably define all the methods of 'Algebra.Ring.C' for
@IntegerFunction a@ (satisfying good semantics),
but it is impossible to define non-bottom instances of 'Eq' and 'Show'.
In general, superclass relationship should indicate
some semantic connection between the two classes.
.
[3] In a few cases, there is a mix of semantic operations and
representation-specific operations.
'toInteger', 'toRational',
and the various operations in 'RealFloating' ('decodeFloat', ...)
are the main examples.
.
[4] In some cases, the hierarchy is not finely-grained enough:
Operations that are often defined independently are lumped together.
For instance, in a financial application one might want a type \"Dollar\",
or in a graphics application one might want a type \"Vector\".
It is reasonable to add two Vectors or Dollars,
but not, in general, reasonable to multiply them.
But the programmer is currently forced to define a method for '(*)'
when she defines a method for '(+)'.
.
In specifying the semantics of type classes,
I will state laws as follows:
.
> (a + b) + c === a + (b + c)
.
The intended meaning is extensional equality:
The rest of the program should behave in the same way
if one side is replaced with the other.
Unfortunately, the laws are frequently violated by standard instances;
the law above, for instance, fails for 'Float':
.
> (1e20 + (-1e20)) + 1.0 = 1.0
> 1e20 + ((-1e20) + 1.0) = 0.0
.
For inexact number types like floating point types,
thus these laws should be interpreted as guidelines rather than absolute rules.
In particular, the compiler is not allowed to use them for optimization.
Unless stated otherwise, default definitions should also be taken as laws.
.
Thanks to Brian Boutel, Joe English, William Lee Irwin II, Marcin
Kowalczyk, Ketil Malde, Tom Schrijvers, Ken Shan, and Henning
Thielemann for helpful comments.
.
.
Usage:
.
Write modules in the following style:
.
> [-# NoImplicitPrelude #-]
> module MyModule where
>
> ... various specific imports ...
>
> import NumericPrelude
.
Importing @NumericPrelude@ is almost the same as
.
> import NumericPrelude.Numeric
> import NumericPrelude.Base .
.
Instead of the @NoImplicitPrelude@ pragma
you could also write @import Prelude ()@
but this will yield problems with numeric literals.
.
.
Scope & Limitations\/TODO:
.
* It might be desireable to split Ord up into Poset and Ord
(a total ordering).
This is not addressed here.
.
* In some cases, this hierarchy may not yet be fine-grained enough.
For instance, time spans (\"5 minutes\") can be added to times (\"12:34\"),
but two times are not addable. (\"12:34 + 8:23\")
As it stands,
users have to use a different operator for adding time spans to times
than for adding two time spans.
Similar issues arise for vector space et al.
This is a consciously-made tradeoff, but might be changed.
This becomes most serious when dealing with quantities with units
like @length\/distance^2@, for which @(*)@ as defined here is useless.
(One way to see the issue: should
@ f x y = iterate (x *) y @
have principal type
@ (Ring.C a) => a -> a -> [a] @
or something like
@ (Ring.C a, Module a b) => a -> b -> [b] @
?)
.
* I stuck with the Haskell 98 names.
In some cases I find them lacking.
Neglecting backwards compatibility, we have renamed classes as follows:
Num --> Additive, Ring, Absolute
Integral --> ToInteger, IntegralDomain, RealIntegral
Fractional --> Field
Floating --> Algebraic, Transcendental
Real --> ToRational
RealFrac --> RealRing, RealField
RealFloat --> RealTranscendental
.
.
Additional standard libraries might include Enum, IEEEFloat (including
the bulk of the functions in Haskell 98's RealFloat class),
VectorSpace, Ratio, and Lattice.
Tested-With: GHC==6.4.1, GHC==6.8.2
Cabal-Version: >=1.6
Build-Type: Simple
Extra-Source-Files:
Makefile
docs/NOTES
docs/README
src/Algebra/GenerateRules.hs
Flag splitBase
description: Choose the new smaller, split-up base package.
Flag buildTests
description: Build test executables
default: False
Source-Repository this
Tag: 0.2
Type: darcs
Location: http://code.haskell.org/numeric-prelude/
Source-Repository head
Type: darcs
Location: http://code.haskell.org/numeric-prelude/
Library
Build-Depends:
parsec >=1 && <4,
QuickCheck >=1 && <3,
storable-record >=0.0.1 && <0.1,
non-negative >=0.0.5 && <0.2,
utility-ht >=0.0.4 && <0.1
If flag(splitBase)
Build-Depends:
base >= 2 && <6,
array >=0.1 && <0.4,
containers >=0.1 && <0.4,
random >=1.0 && <1.1
Else
Build-Depends: base >= 1.0 && < 2
GHC-Options: -Wall
Hs-source-dirs: src
Exposed-modules:
Algebra.Absolute
Algebra.Additive
Algebra.Algebraic
Algebra.Differential
Algebra.DimensionTerm
Algebra.DivisibleSpace
Algebra.Field
Algebra.Indexable
Algebra.IntegralDomain
Algebra.NonNegative
Algebra.Lattice
Algebra.Laws
Algebra.Module
Algebra.ModuleBasis
Algebra.Monoid
Algebra.NormedSpace.Euclidean
Algebra.NormedSpace.Maximum
Algebra.NormedSpace.Sum
Algebra.OccasionallyScalar
Algebra.PrincipalIdealDomain
Algebra.RealField
Algebra.RealIntegral
Algebra.RealRing
Algebra.RealTranscendental
Algebra.RightModule
Algebra.Ring
Algebra.ToInteger
Algebra.ToRational
Algebra.Transcendental
Algebra.Units
Algebra.Vector
Algebra.VectorSpace
Algebra.ZeroTestable
MathObj.Algebra
MathObj.DiscreteMap
MathObj.LaurentPolynomial
MathObj.Matrix
MathObj.Monoid
MathObj.PartialFraction
MathObj.Permutation
MathObj.Permutation.CycleList
MathObj.Permutation.CycleList.Check
MathObj.Permutation.Table
MathObj.Polynomial
MathObj.Polynomial.Core
MathObj.PowerSeries
MathObj.PowerSeries.Core
MathObj.PowerSeries.DifferentialEquation
MathObj.PowerSeries.Example
MathObj.PowerSeries.Mean
MathObj.PowerSeries2
MathObj.PowerSeries2.Core
MathObj.PowerSum
MathObj.RefinementMask2
MathObj.RootSet
Number.Complex
Number.DimensionTerm
Number.DimensionTerm.SI
Number.FixedPoint
Number.FixedPoint.Check
Number.GaloisField2p32m5
Number.NonNegative
Number.NonNegativeChunky
Number.PartiallyTranscendental
Number.Peano
Number.Positional
Number.Positional.Check
Number.Quaternion
Number.Ratio
Number.ResidueClass
Number.ResidueClass.Check
Number.ResidueClass.Maybe
Number.ResidueClass.Func
Number.ResidueClass.Reader
Number.OccasionallyScalarExpression
Number.SI.Unit
Number.SI
Number.Physical.Unit
Number.Physical.UnitDatabase
Number.Physical
Number.Physical.Read
Number.Physical.Show
NumericPrelude.List.Checked
NumericPrelude.List.Generic
NumericPrelude.Elementwise
NumericPrelude.Numeric
NumericPrelude.Base
NumericPrelude
Other-modules:
NumericPrelude.List
Algebra.AffineSpace
MathObj.Gaussian.Variance
MathObj.Gaussian.Bell
MathObj.Gaussian.Polynomial
-- I think I won't add them this way.
-- It is certainly better to split the class into comparison and selection.
Algebra.EqualityDecision
Algebra.OrderDecision
Executable test
Hs-Source-Dirs: src, test
Main-Is: Test.hs
If !flag(buildTests)
Buildable: False
Executable testsuite
Hs-Source-Dirs: src, test
GHC-Options: -Wall
Other-modules:
Test.NumericPrelude.Utility
Test.Number.GaloisField2p32m5
Test.MathObj.RefinementMask2
Test.MathObj.PartialFraction
Test.MathObj.Matrix
Test.MathObj.Polynomial
Test.MathObj.PowerSeries
Test.MathObj.Gaussian.Variance
Test.MathObj.Gaussian.Bell
Test.MathObj.Gaussian.Polynomial
Main-Is: Test/Run.hs
If flag(buildTests)
Build-Depends: HUnit >=1 && <2
Else
Buildable: False
Executable test-gaussian
Hs-Source-Dirs: src, test
Main-Is: Gaussian.hs
Other-Modules:
MathObj.Gaussian.Example
If flag(buildTests)
Build-Depends:
gnuplot >=0.3 && <0.5,
HTam >=0.0.2 && <0.1
Else
Buildable: False