# scientific

Numbers represented using scientific notation https://github.com/basvandijk/scientific

LTS Haskell 13.17: | 0.3.6.2 |

Stackage Nightly 2019-04-19: | 0.3.6.2 |

Latest on Hackage: | 0.3.6.2 |

**Bas van Dijk**

**Bas van Dijk**

#### Module documentation for 0.3.6.2

- Data
- Data.ByteString
- Data.ByteString.Builder

- Data.Scientific
- Data.Text
- Data.Text.Lazy
- Data.Text.Lazy.Builder

- Data.Text.Lazy

- Data.ByteString

`Data.Scientific`

provides the number type `Scientific`

. Scientific numbers are
arbitrary precision and space efficient. They are represented using
scientific notation.
The implementation uses a coefficient `c :: `

and a base-10 exponent
`Integer`

`e :: `

. A scientific number corresponds to the
`Int`

`Fractional`

number:

.`fromInteger`

c * 10 `^^`

e

Note that since we're using an `Int`

to represent the exponent these numbers
aren't truly arbitrary precision. I intend to change the type of the exponent
to `Integer`

in a future release.

The main application of `Scientific`

is to be used as the target of parsing
arbitrary precision numbers coming from an untrusted source. The advantages
over using `Rational`

for this are that:

A

`Scientific`

is more efficient to construct. Rational numbers need to be constructed using`%`

which has to compute the`gcd`

of the`numerator`

and`denominator`

.`Scientific`

is safe against numbers with huge exponents. For example:`1e1000000000 ::`

will fill up all space and crash your program. Scientific works as expected:`Rational`

`read "1e1000000000" :: Scientific`

`1.0e1000000000`

Also, the space usage of converting scientific numbers with huge exponents to

(like:`Integral`

s`Int`

) or

(like:`RealFloat`

s`Double`

or`Float`

) will always be bounded by the target type.

## Changes

* Due to a regression introduced in 0.3.4.14 the RealFrac methods

and floatingOrInteger became vulnerable to a space blowup when

applied to scientifics with huge exponents. This has now been

fixed again.

0.3.6.1

* Fix build on GHC < 8.

0.3.6.0

* Make the methods of the Hashable, Eq and Ord instances safe to

use when applied to scientific numbers coming from untrusted

sources. Previously these methods first converted their arguments

to Rational before applying the operation. This is unsafe because

converting a Scientific to a Rational could fill up all space and

crash your program when the Scientific has a huge base10Exponent.

Do note that the hash computation of the Hashable Scientific

instance has been changed because of this improvement!

Thanks to Tom Sydney Kerckhove (@NorfairKing) for pushing me to

fix this.

* fromRational :: Rational -> Scientific now throws an error

instead of diverging when applied to a repeating decimal. This

does mean it will consume space linear in the number of digits of

the resulting scientific. This makes "fromRational" and the other

Fractional methods "recip" and "/" a bit safer to use.

* To get the old unsafe but more efficient behaviour the following

function was added: unsafeFromRational :: Rational -> Scientific.

* Add alternatives for fromRationalRepetend:

fromRationalRepetendLimited

:: Int -- ^ limit

-> Rational

-> Either (Scientific, Rational)

(Scientific, Maybe Int)

and:

fromRationalRepetendUnlimited

:: Rational -> (Scientific, Maybe Int)

Thanks to Ian Jeffries (@seagreen) for the idea.

0.3.5.3

* Dropped upper version bounds of dependencies

because it's to much work to maintain.

0.3.5.2

* Remove unused ghc-prim dependency.

* Added unit tests for read and scientificP

0.3.5.1

* Replace use of Vector from vector with Array from primitive.

0.3.5.0

* Export scientificP :: ReadP Scientific

(Courtesy of Shlok Datye @shlok)

0.3.4.15

* Fix build for base < 4.8.

0.3.4.14

* Some minor performance improvements.

0.3.4.13

* Support criterion-1.2

0.3.4.12

* Support base-4.10

0.3.4.11

* Support tasty-ant-xml-1.1.0

0.3.4.10

* Tighten lower bound on vector from 0.5 to 0.7 because building with

vector < 0.7 results in a build error.

* Move the internal modules Math.NumberTheory.Logarithms and

GHC.Integer.Logarithms.Compat to their own package integer-logarithms so

other people can share that code.

0.3.4.9

* Support QuickCheck-2.9.

0.3.4.8

* Make bytestring-builder's installation conditional based on a Cabal flag.

0.3.4.7

* Unconditionally export Data.ByteString.Builder.Scientific.

The bytestring-builder cabal flag has been removed.

Depend on bytestring-builder for backwards compatibility for GHC < 7.8.

0.3.4.6

* Made toDecimalDigits more similar to floatToDigits

Previously:

toDecimalDigits 0 == ([0],1)

Now:

toDecimalDigits 0 == ([0],0)

Because:

Numeric.floatToDigits 10 (0 :: Double) == ([0],0)

* Introduce a special case for 0 in fromFloatDigits

fromFloatDigits 0 = 0

This should fix https://github.com/bos/aeson/issues/369

0.3.4.5

The following are all a courtesy of Oleg Grenrus (phadej):

* Support GHC-8.0.1

* Support binary-0.8

* Enable Travis continuous integration

0.3.4.4

* Improved performance of toDecimalDigits by 13%.

0.3.4.3

* Fix build with integer-simple.

0.3.4.2

* Fix build on GHC-7.4.

Courtesy of Adam Bergmark..

0.3.4.1

* Fix build on GHC-7.0.4

0.3.4.0

* Added fromRationalRepetend & toRationalRepetend

for safely converting from and to rationals

which have a repeating decimal representation like:

1 % 28 = 0.03(571428).

* Added a Binary instance.

* Various performance improvements.

* Support vector-0.11

* Support tasty-0.11

* Support criterion-1.1.0.0

0.3.3.8

* Support QuickCheck-2.8.

0.3.3.7

* Fixed both the

Prelude Data.Scientific> reads "0.0" :: [(Data.Scientific.Scientific,String)]

[(0.0,".0"),(0.0,"")]

problem and the

read " 8" :: Scientific fails, while read " 8" :: Double succeeds

problem.

Courtesy of neongreen.

0.3.3.6

* Fixed bug in the x / y method for Scientific. Since I was using

the default implementation: `x * recip y` the operation would

diverge when `recip y` had an infinite decimal output.

This shouldn't happen when the result of / is finite again.

For example: 0.6 / 0.3 should yield 2.0.

This is now fixed by using the following implementation:

`x / y = fromRational $ toRational x / toRational y`

0.3.3.5

* Fixed bug when converting the Scientific:

`scientific 0 someBigExponent` to a bounded Integral using toBoundedInteger

or to a bounded RealFloat using toBoundedRealFloat.

If someBigExponent was big enough to trigger the big-exponent protection

the beforementioned functions didn't return 0.

This is fixed by explicitly handling a coefficient of 0.

0.3.3.4

* Relax upper version bounds of base and deepseq

for the test suite and benchmarks.

0.3.3.3

* Add support for `deepseq-1.4`.

0.3.3.2

* Fix parsing of empty digit string (#21).

0.3.3.1

* Allow newer tasty, tasty-hunit and criterion.

0.3.3.0

* Add the isFloating or isInteger predicates.

Courtesy of Zejun Wu (@watashi).

* Add the toRealFloat' and toBoundedInteger functions.

Courtesy of Fujimura Daisuke (@fujimura).

0.3.2.2

* Enable package to link with integer-simple instead of

integer-gmp using the -finteger-simple cabal flag.

Courtesy of @k0ral.

0.3.2.1

* Parameterize inclusion of the Data.ByteString.Builder.Scientific

module using the bytestring-builder flag. Disabling this flag

allows building on GHC-7.0.4 which has bytestring-0.9 installed

by default.

0.3.2.0

* Add the floatingOrInteger function

* Fix build on GHC-7.0.4

* More efficient and better behaving magnitude computation

* Lower the number of cached magnitudes to 324 (same as GHC.Float)

0.3.1.0

* Don't normalize on construction but do it when pretty-printing

instead. Also provide a manual normalize function.

* Improve efficiency of toRealFloat

* Added note about caching magnitudes

* Dropped dependency on arithmoi

* Make benchmark easier to build

* Add junit XML output support (for Jenkins)

0.3.0.2

* Lower the minimal QuickCheck version.

* Make sure sized exponents are generated in the QuickCheck tests.

0.3.0.1

* Fix build for bytestring-0.10.0.*

0.3.0.0

* Fix a DoS vulnerability that allowed an attacker to crash the

process by sending a scientific with a huge exponent like

1e1000000000.

* Fix various RealFrac methods.

* Cache some powers of 10 to speed up the magnitude computation.

* Normalize scientific numbers on construction.

* Move the Text Builder to its own module &

provide a ByteString builder

* Added more documentation

0.2.0.2

* Widen the dreaded pointlessly tight upper bounds

0.2.0.1

* Support the latest versions of smallcheck and tasty

0.2.0.0

* added deriving data

0.1.0.1

* Loosen upper bounds on package versions

0.1.0.0

* Fixed bugs & Changed API

0.0.0.2

* Support building the library on GHC >= 7.0.1

0.0.0.1

* Simplification in the Show instance

* Optimization in fromRealFloat

0.0.0.0

* Initial commit

**and many more**