Cookbook/Numbers
From HaskellWiki
(Difference between revisions)
(Added the "round 2.5" example and "truncate") |
(Added "adding complex numbers") |
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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> | ||
| Line 94: | Line 94: | ||
| [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> | ||
|} | |} | ||
Revision as of 14:49, 6 August 2009
Numbers in Haskell can be of the typeInt, Integer, Float, Double, or Rational
Contents |
1 Rounding numbers
| Problem | Solution | Examples |
|---|---|---|
| rounding | round | round 3.4 --> 3 round 3.5 --> 4 round 2.5 --> 2 |
finding the nearest integer greater than or equal to x
| ceiling | ceiling 3.0 --> 3 ceiling 3.1 --> 4 |
finding the nearest integer less than or equal to x
| floor | floor 3.0 --> 3 floor 3.9 --> 3 |
finding the nearest integer between zero and x
| 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 import Data.List (foldl') -- Extract a range of bits, most-significant first bitRange :: Bits a => a -> Int -> Int -> [Bool] bitRange n lo hi = foldl' (\l -> \x -> testBit n x : l) [] [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 |
