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Numbers in Haskell can be of the type <hask>Int, Integer, Float, Double, or Rational</hask>.
Numbers in Haskell can be of the type <hask>Int, Integer, Float, Double, or Rational</hask>.
-
= Rounding numbers =
+
== Rounding numbers ==
{| class="wikitable"
{| class="wikitable"
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! Examples
! Examples
|-
|-
-
| rounding
+
| rounding a given number
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v:round round]
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v:round round]
|<haskell>
|<haskell>
round 3.4 --> 3
round 3.4 --> 3
round 3.5 --> 4
round 3.5 --> 4
 +
round 2.5 --> 2
</haskell>
</haskell>
|-
|-
-
| find the nearest integer greaterthan or equal to <code>x</code>
+
| finding the nearest integer greater than or equal to a given number
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3Aceiling ceiling]
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3Aceiling ceiling]
|<haskell>
|<haskell>
 +
ceiling 3.0 --> 3
ceiling 3.1 --> 4
ceiling 3.1 --> 4
</haskell>
</haskell>
|-
|-
-
| find the nearest integer less than or equal to <code>x</code>
+
| finding the nearest integer less than or equal to a given number
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3Afloor floor]
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3Afloor floor]
|<haskell>
|<haskell>
-
floor 3.5 --> 3
+
floor 3.0 --> 3
 +
floor 3.9 --> 3
 +
</haskell>
 +
|-
 +
| finding the nearest integer between zero and a given number
 +
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3Atruncate truncate]
 +
|<haskell>
 +
truncate 3.0 --> 3
 +
truncate 3.9 --> 3
 +
truncate (negate 3.0) --> -3
 +
truncate (negate 3.9) --> -3
</haskell>
</haskell>
|}
|}
-
=Taking logarithms =
+
== Taking logarithms ==
<haskell>
<haskell>
log 2.718281828459045 --> 1.0
log 2.718281828459045 --> 1.0
Line 35: Line 47:
</haskell>
</haskell>
-
= Generating random numbers =
+
== Generating random numbers ==
<haskell>
<haskell>
import System.Random
import System.Random
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</haskell>
</haskell>
-
= Binary representation of numbers =
+
== Binary representation of numbers ==
<haskell>
<haskell>
import Data.Bits
import Data.Bits
-
import Data.List (foldl')
 
-- Extract a range of bits, most-significant first
-- Extract a range of bits, most-significant first
bitRange :: Bits a => a -> Int -> Int -> [Bool]
bitRange :: Bits a => a -> Int -> Int -> [Bool]
-
bitRange n lo hi = foldl' (\l -> \x -> testBit n x : l) [] [lo..hi]
+
bitRange n lo hi = reverse . map (testBit n) [lo..hi]
-- Extract all bits, most-significant first
-- Extract all bits, most-significant first
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</haskell>
</haskell>
-
= Using complex numbers =
+
== Using complex numbers ==
{| class="wikitable"
{| class="wikitable"
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| [http://haskell.org/ghc/docs/latest/html/libraries/base/Data-Complex.html#v%3A%3A%2B (:+)]
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Data-Complex.html#v%3A%3A%2B (:+)]
|<haskell>
|<haskell>
-
import Complex
+
import Data.Complex
1.0 :+ 0.0 --> 1.0 :+ 0.0
1.0 :+ 0.0 --> 1.0 :+ 0.0
</haskell>
</haskell>
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| [http://haskell.org/ghc/docs/latest/html/libraries/base/Data-Complex.html#v%3AmkPolar mkPolar]
| [http://haskell.org/ghc/docs/latest/html/libraries/base/Data-Complex.html#v%3AmkPolar mkPolar]
|<haskell>
|<haskell>
-
import Complex
+
import Data.Complex
mkPolar 1.0 pi --> (-1.0) :+ 1.2246063538223773e-16
mkPolar 1.0 pi --> (-1.0) :+ 1.2246063538223773e-16
 +
</haskell>
 +
|-
 +
| adding complex numbers
 +
|
 +
|<haskell>
 +
import Data.Complex
 +
(1 :+ 1) + (2 :+ 2) --> 3.0 :+ 3.0
</haskell>
</haskell>
|}
|}

Current revision

Numbers in Haskell can be of the type
Int, Integer, Float, Double, or Rational
.

Contents

1 Rounding numbers

Problem Solution Examples
rounding a given number round 
round 3.4      --> 3
round 3.5      --> 4
round 2.5      --> 2
finding the nearest integer greater than or equal to a given number ceiling 
ceiling 3.0    --> 3
ceiling 3.1    --> 4
finding the nearest integer less than or equal to a given number floor 
floor 3.0      --> 3
floor 3.9      --> 3
finding the nearest integer between zero and a given number truncate 
truncate 3.0           -->  3
truncate 3.9           -->  3
truncate (negate 3.0)  --> -3
truncate (negate 3.9)  --> -3

2 Taking logarithms 

log 2.718281828459045  --> 1.0
logBase 10 10000       --> 4.0

3 Generating random numbers 

import System.Random
 
main = do
  gen <- getStdGen
  let ns = randoms gen :: [Int]
  print $ take 10 ns

4 Binary representation of numbers 

import Data.Bits
 
-- Extract a range of bits, most-significant first
bitRange :: Bits a => a -> Int -> Int -> [Bool]
bitRange n lo hi = reverse . map (testBit n) [lo..hi]
 
-- Extract all bits, most-significant first
bits :: Bits a => a -> [Bool]
bits n = bitRange n 0 (bitSize n - 1)
 
-- Display a number in binary, including leading zeroes.
-- c.f. Numeric.showHex
showBits :: Bits a => a -> ShowS
showBits = showString . map (\b -> if b then '1' else '0') . bits

5 Using complex numbers

Problem Solution Examples
creating a complex number from real and imaginary rectangular components (:+) 
import Data.Complex
1.0 :+ 0.0        --> 1.0 :+ 0.0
creating a complex number from polar components mkPolar 
import Data.Complex
mkPolar 1.0 pi    --> (-1.0) :+ 1.2246063538223773e-16
adding complex numbers 
import Data.Complex
(1 :+ 1) + (2 :+ 2) --> 3.0 :+ 3.0
Retrieved from "http://www.haskell.org/haskellwiki/Cookbook/Numbers"