Cookbook/Numbers
From HaskellWiki
< Cookbook(Difference between revisions)
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<haskell> | <haskell> | ||
import Data.Bits | import Data.Bits | ||
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-- 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 = | + | bitRange n lo hi = reverse . map (testBit n) [lo..hi] |
-- Extract all bits, most-significant first | -- Extract all bits, most-significant first | ||
Current revision
Numbers in Haskell can be of the typeInt, 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 |
