CODEWITHSUNDEEP
haskellprecision
MYV
MYV

Reputation: 4544

High precision floating point numbers in Haskell?

I know Haskell has native data types which allow you to have really big integers so things like 

>> let x = 131242358045284502395482305
>> x
131242358045284502395482305

work as expected. I was wondering if there was a similar "large precision float" native structure I could be using, so things like

>> let x = 5.0000000000000000000000001
>> x
5.0000000000000000000000001

could be possible. If I enter this in Haskell, it truncates down to 5 if I go beyond 15 decimal places (double precision).

Upvotes: 28

Views: 16157

Answers (4)

jberryman
jberryman

Reputation: 16645

I believe the standard package for arbitrary precision floating point numbers is now https://hackage.haskell.org/package/scientific

Upvotes: 1

Mekeor Melire
Mekeor Melire

Reputation: 522

Haskell does not have high-precision floating-point numbers naitively.

For a package/module/library for this purpose, I'd refer to this answer to another post. There's also an example which shows how to use this package, called numbers.

Upvotes: 9

L29Ah
L29Ah

Reputation: 298

If you need a high precision /fast/ floating point calculations, you may need to use FFI and long doubles, as the native Haskell type is not implemented yet (see https://ghc.haskell.org/trac/ghc/ticket/3353).

Upvotes: 1

Thomas M. DuBuisson
Thomas M. DuBuisson

Reputation: 64740

Depending on exactly what you are looking for:

  • Float and Double - pretty much what you know and "love" from Floats and Doubles in all other languages.
  • Rational which is a Ratio of Integers
  • FixedPoint - This package provides arbitrary sized fixed point values. For example, if you want a number that is represented by 64 integral bits and 64 fractional bits you can use FixedPoint6464. If you want a number that is 1024 integral bits and 8 fractional bits then use $(mkFixedPoint 1024 8) to generate type FixedPoint1024_8.
  • EDIT: And yes, I just learned about the numbers package mentioned above - very cool.

Upvotes: 22

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