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Add Haskell examples
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‎Haskell/1-comments.hs‎

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-- Single comment.
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{-
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Multiline
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comments.
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-}

‎Haskell/2-let-where.hs‎

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globalX = 5
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main = do
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-- Use the global definition.
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print globalX -- 5
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-- Define a constant localX with the value 6.
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let localX = 6
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print localX -- 6
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-- Multiline let.
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let addX = 7
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newX = localX + addX
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print newX -- 13
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-- Define constants with 'where' syntax.
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let newY = localY + addY
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where
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localY = 8
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addY = 9
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print newY -- 17

‎Haskell/4-types.hs‎

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import Text.Printf(printf)
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main = do
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-- Built-in types
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-- Singnature specification '::' is optional.
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-- In the case of ambiguity like Integer vs Int or Double vs Float
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-- default types Integer or Double will be used.
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let integer = 5 :: Integer
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int = 5 :: Int
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double = 10.3 :: Double
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float = 10.3 :: Float
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char = 'c' :: Char
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string1 = "Hello" :: String -- String and [Char] are the same
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string2 = "Hello" :: [Char] -- String and [Char] are the same
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bool = True :: Bool
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print integer -- 5
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print int -- 5
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print double -- 10.3
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print float -- 10.3
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print char -- 'c'
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print string1 -- "Hello"
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print string2 -- "Hello"
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print bool -- True
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-- Tuples
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let person = ("Marcus Aurelius", 121, "Roma", "emperor")
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(_, _, city, _) = person -- _ means discard the value
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print person -- ("Marcus Aurelius", 121, "Roma", "emperor")
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print city -- "Roma"
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let point = (20, 30) :: (Int, Int)
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x = fst point
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y = snd point
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print point
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printf "%v %v" x y
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let cities = ["Athens", "Roma", "London", "Beijing", "Kiev", "Riga"]
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cities' = cities ++ ["Odessa"] -- ' is the valid character in the name
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cities'' = "New York" : cities'
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cities''' = tail cities''
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cities'''' = init cities'''
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print cities -- ["Athens","Roma","London","Beijing","Kiev","Riga"]
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print cities' -- ["Athens","Roma","London","Beijing","Kiev","Riga","Odessa"
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print cities'' -- ["New York","Athens","Roma","London","Beijing","Kiev","Riga","Odessa"]
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print cities''' -- ["Athens","Roma","London","Beijing","Kiev","Riga","Odessa"]
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print cities'''' -- ["Athens","Roma","London","Beijing","Kiev","Riga"]

‎Haskell/5-NaN-Infinity.hs‎

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main = do
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let count = 0 / 0
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print count
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print (1 / 0)
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print (-1 / 0)

‎Haskell/6-read.hs‎

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import Data.Char (isHexDigit, ord)
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import Numeric (readInt, readFloat, readOct, readDec, readHex, readSigned)
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import Text.Printf (printf)
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main = do
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print $ readInt 2 (`elem` "01") (\x -> ord x - ord '0') "11" -- [(3, "")]
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-- The same as 'print (readOct "11")'.
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print $ readOct "11" -- [(9, "")]
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print $ readDec "5" -- [(5, "")]
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print $ readDec "+5" -- []
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print $ readDec "-5" -- []
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print $ readDec "5mm" -- [(5, "mm")]
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print $ readSigned readDec "5" -- [(5, "")]
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print $ readSigned readDec "+5" -- []
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print $ readSigned readDec "-5" -- [(-5, "")]
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print $ readSigned readDec "5mm" -- [(5, "mm")]
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print $ readDec "(5)" -- []
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print $ readDec "\"5\"" -- []
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print $ readDec "[5]" -- []
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print $ readDec "NaN" -- []
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print $ readDec "Infinity" -- []
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print $ readDec "-Infinity" -- []
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-- Type specification is required to resolve the ambiguity of whether we should read Int or Integer.
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print $ readDec "5.1"
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-- 5.1 [(5, ".1")]
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print $ readDec "5.1e50"
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-- 5.1 [(5, ".1e50")]
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print $ readDec "0.000000000005"
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-- [(0, ".000000000005")]
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print $ readDec "0.0000005"
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-- [(0, ".0000005")]
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print $ readDec "0.000005"
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-- [(0, ".0000005")]
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print $ readHex "fF" -- [(255, "")]
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print $ readHex "0xff" -- [(0, "xff")]
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print $ readHex "0xFf" -- [(0, "xFf")]
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print $ readHex " 0xFf " -- []
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print $ readInt 2 (`elem` "01") (\x -> ord x - ord '0') "ff" -- []
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print $ readOct "ff" -- []
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print $ readDec "ff" -- []
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print $ readHex "ff" -- [(255, "")]
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let readHexDigit x = fst $ head $ readHex [x]
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print $ readInt 16 isHexDigit readHexDigit "ff" -- [(255, "")]
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print $ readInt 17 isHexDigit readHexDigit "ff" -- [(270, "")]
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print $ readInt 20 isHexDigit readHexDigit "ff" -- [(315, "")]
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print $ readInt 30 isHexDigit readHexDigit "ff" -- [(465, "")]
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print $ readInt 31 isHexDigit readHexDigit "ff" -- [(480, "")]
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print $ readInt 32 isHexDigit readHexDigit "ff" -- [(495, "")]
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print $ readInt 33 isHexDigit readHexDigit "ff" -- [(510, "")]
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print $ readInt 34 isHexDigit readHexDigit "ff" -- [(525, "")]
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print $ readInt 35 isHexDigit readHexDigit "ff" -- [(540, "")]
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print $ readInt 36 isHexDigit readHexDigit "ff" -- [(555, "")]
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print $ readInt 37 isHexDigit readHexDigit "ff" -- [(570, "")]
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print $ readFloat "3.14" -- [(3.14, "")]
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print $ readFloat "314e-2" -- [(3.14, "")]
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print $ readFloat "3.14text" -- [(3.14, "text")]
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print $ readFloat "0.0314E+2" -- [(3.14, "")]
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print $ readFloat "5" -- [(5.0, "")]
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print $ readFloat "5.0" -- [(5.0, "")]
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print $ readFloat "5.0000000000000001" -- [(5.0, "")]
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print $ readFloat "5.1" -- [(5.1, "")]
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print $ readFloat "5.000000000000001" -- [(5.000000000000001, "")]
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print $ readFloat "100" -- [(100, "")]
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print $ readSigned readFloat "-100" -- [(-100, "")]
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print $ readFloat "+100" -- []
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print $ readFloat "5" -- [(5, "")]
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print $ readFloat "+5" -- []
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print $ readFloat "5mm" -- [(5, "mm")]
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print $ readFloat "(5)" -- []
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print $ readFloat "\"5\"" -- []
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print $ readFloat "[5]" -- []
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print $ readFloat "NaN" -- []
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print $ readFloat "Infinity" -- []
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print $ readFloat "-Infinity" -- []

‎Haskell/8-bitwise.hs‎

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import Data.Char (chr, ord)
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import Data.Bits ((.&.), (.|.), xor, complement, shift, shiftL, shiftR, rotate)
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import Numeric (showIntAtBase, showSigned)
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import Text.Printf(printf)
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main = do
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let toBinary :: Int -> String
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toBinary n = showSigned (showIntAtBase 2 toBinDigit) 0 n ""
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where toBinDigit d = chr (ord '0' + d)
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let a = 9
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b = 14
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c = -9
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let aBinary = toBinary a
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bBinary = toBinary b
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cBinary = toBinary c
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printf "%v to base 2: %v\n" a aBinary
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printf "%v to base 2: %v\n" b bBinary
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print "Bitwise operators"
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printf "%v .&. %v = %v\n" a b $ a .&. b
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printf "%v .&. %v = %v\n" aBinary bBinary $ toBinary $ a .&. b
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printf "%v .|. %v = %v\n" a b $ a .|. b
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printf "%v .|. %v = %v\n" aBinary bBinary $ toBinary $ a .|. b
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printf "%v `xor` %v = %v\n" a b $ a `xor` b
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printf "%v `xor` %v = %v\n" aBinary bBinary $ toBinary $ a `xor` b
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printf "complement %v = %v\n" a $ complement a
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printf "complement %v = %v\n" aBinary $ toBinary $ complement a
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printf "%v `shiftL` 2 = %v\n" a $ a `shiftL` 2
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printf "%v `shiftL` 2 = %v\n" aBinary $ toBinary $ a `shiftL` 2
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printf "%v `shiftR` 2 = %v\n" b $ b `shiftR` 2
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printf "%v `shiftR` 2 = %v\n" bBinary $ toBinary $ b `shiftR` 2
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printf "%v `shift` 2 = %v\n" a $ a `shift` 2
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printf "%v `shift` 2 = %v\n" aBinary $ toBinary $ a `shift` 2
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printf "%v `shift` (-2) = %v\n" b $ b `shift` (-2)
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printf "%v `shift` (-2) = %v\n" bBinary $ toBinary $ b `shift` (-2)
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printf "%v `rotate` 2 = %v\n" b $ b `rotate` 2
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printf "%v `rotate` 2 = %v\n" b $ toBinary $ b `rotate` 2
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printf "%v `rotate` (-2) = %v\n" c $ c `rotate` (-2)
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printf "%v `rotate` (-2) = %v\n" c $ toBinary $ c `rotate` (-2)

‎Haskell/9-bigint.hs‎

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import Text.Printf(printf)
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import Data.List(sort)
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main = do
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let maxInt = maxBound :: Int
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integer = fromIntegral maxInt :: Integer
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printf "maxInt = %v\n" (maxInt :: Int)
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printf "maxInt + 1 = %v\n" (maxInt + 1 :: Int)
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printf "maxInt + 2 = %v\n" (maxInt + 2 :: Int)
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putStrLn ""
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printf "maxInt = %v\n" maxInt
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printf "integer = %v\n" integer
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putStrLn ""
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printf "fromIntegral maxInt == integer: %v\n"
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$ show
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$ fromIntegral maxInt
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== integer
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putStrLn ""
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printf "integer = %v\n" integer
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printf "integer + 1 = %v\n" $ integer + 1
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printf "integer + 2 = %v\n" $ integer + 2
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putStrLn ""
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printf "15 `div` 3 = %v\n" (15 `div` 3 :: Int)
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printf "3 `div` 2 = %v\n" (3 `div` 2 :: Int)
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-- printf "3 / 2 = %v\n" (3 / 2 :: Int)
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-- Doesn't compile because operator / isn't defined for Int and Integer.
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-- let a = 1.5 :: Integer
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-- Doesn't compile because Fractional can't be converted to Integer.
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printf "(1000 ^ 200) / 12321 = %v\n" (1000 ^ 200 `div` 12321 :: Integer)
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putStrLn ""
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let array2 = [3, -2, 7, -5, -1, 2, 5, 0] :: [Integer]
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print array2
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print $ sort array2
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putStrLn ""
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let array1 :: Num a => [a]
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array1 = [-2, 7, 1, 3, -2, 8, 5, -4]
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print (array1 :: [Integer])
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print $ sort (array1 :: [Int])
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print $ sort (array1 :: [Integer])

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