1 排版规则
反引号能够将一个命令的标准输出插在一个命令行中任何位置
A `plus` asd
Unix 使用/ 左斜杠 windows使用\斜杠
和等号对齐非常重要；
以下是错误例子 未对齐；
常用关键字
导入模块
:module +Data.List
import Data.Char (digitToInt)
:module +Data.Char
:unset +m 取消输入多行；
:t add 可以得到函数类型
:set +m 可以输入多行；
Cmd 命令行下 runghc file.hs
\
列表和元组的区别 即
[1,2,3] 和 (1,”2”, 三)的区别..
[1,2..5] 省略号定义数组二个冒号；
1:[1,2] 前增扩展数组。。
IO
<- 将 io string 转换为string .
:cd d:\haskexam
Prelude> saf<-readFile "output.txt"
saf :: String
saf
"E23E4QWREWQRWQR\n"
ad<-getLine 可以让用户输入ad变量的值
读取文件内容并显示；
readFile "D:\\haskexam\\1.txt"
putStrLn "fas"
fas
LET
let ad="asd" 给变量赋值；
prelude
lines "asd\nadsad"
根据换行符将一个字符串分为多个字符串
length [1,2] 数组的长度
show 1234 将数字转换为字符显示
"1234"
print 213 显示
213
Compare 比较大小
Head 、 tail 、take、drop 、last列表的操作‘
Fst 、snd 元组的操作
定义函数；
定义一个新的数据结构
定义枚举。
data Roygbiv = Red
| Orange
| Yellow
| Green
| Blue
| Indigo
| Violet
deriving (Eq, Show)
报错
error "dasdfas"
*** Exception: dasdfas
Break ：分割列表
碰到奇数分为二个列表；
all &any
all odd [1,3,5]
True
isPrefixOf [2] [2,4]
isSuffixOf "24" "2342t4"
zip [1,2,3] [4,5]
[(1,4),(2,5)]
:module -Data.List
Prelude Data.List>zipWith (+) [1,2,3] [4
[5]
words "das asd asd"
["das","asd","asd"]
unwords ["jumps", "over", "the", "lazy", "dog"]
"jumps over the lazy dog"
let ad = map toLower "D A"
map toUpper "dasd ads"
map negate [1,2,3]
[-1,-2,-3]
map (dropWhile isSpace) [" a","f"," e"]
["a","f","e"]
zip3 "foo" "bar" "quux"
[('f','b','q'),('o','a','u'),('o','r','u')]
map (+3) [24,36]
[27,39]
(`elem` ['a'..'z']) 'f'
True
(init.tail) "fas"
"a"
(init.tails) "fas"
["fas","as","s"]
map isUpper "fdfD"
[False,False,False,True]
isUpper (head "ad")
--多行注释 单行注释；
Prelude> {-
Prelude| asd
Prelude| asd
Prelude| -}
//
:show imports
标准引导库 Prelude.hs
error "fa"
*** Exception: fa
div 4 2
2
Mod
Negate
Abs
'\98'
'b'
1.2e3
1200.0
[2*n | n<-[2..14] , odd n]
[2*n | n<-[2..14] , n>5]
[m+n | (m,n)<-[(1,2),(3,4)] ]
复制；
replicate 3 'f'
"fff"
it :: [Char]
(0.02 secs, 0 bytes)
1:[1]
[1,1]
[1]++[2]
[1,2]
[1,2]!!0
1
concat [[1,2,33],[4,5]]
[1,2,33,4,5]
or [True, False]
True
let x=5 in x^2+2*x
35
let squartwo n m = sqn+sqm
Prelude| where
Prelude| sqn = n*n
Prelude| sqm = m*m
Prelude|
squartwo :: Num a => a -> a -> a
(0.00 secs, 0 bytes)
Prelude> squartwo 2 3
13
sum [2..6]
20
concat ["1","2"]
"12"
let doubleAll xs = [2*x|x<-xs]
Prelude|
doubleAll :: Num t => [t] -> [t]
(0.00 secs, 0 bytes)
Prelude> doubleAll[2,3]
[4,6]
map (+3) [1,2,3]
[4,5,6]
let add a b = a+b
map (add 2) [1,2]
[3,4]
map (replicate 2) [1,2,3]
[[1,1],[2,2],[3,3]]
map fst [(1,2),(3,5),(6,3),(2,6),(2,5)]
[1,3,6,2,2]
[x+3|x<-[1,2,3]]
[4,5,6]
Data.List;
intersperse '_' "faf"
"f_a_f"
intercalate "fs" ["12","34"]
"12fs34"
transpose [[1,2],[3,4],[6,7]]
[[1,3,6],[2,4,7]]
map sum $ transpose [[0,3,5,9],[10,0,0,9],[8,5,1,-1]]
[18,8,6,17]
map sum (transpose [[0,3,5,9],[10,0,0,9],[8,5,1,-1]] )
sum [1,2,5]
8
concat ["24", "3"]
"243"
concat $ map (replicate 4) [1..3]
[1,1,1,1,2,2,2,2,3,3,3,3]
concatMap (replicate 4) [1..3]
[1,1,1,1,2,2,2,2,3,3,3,3]
take 6 $ iterate (*3) 2
[2,6,18,54,162,486]
splitAt 3 "heyman"
("hey","man")
takeWhile (>3) [6,5,4,3,2,1,2,3,4,5,4,3,2,1]
[6,5,4]
'f'/='g'
True
'f'=='g'
False
takeWhile (<10000) $ map (^3) [1..]
[1,8,27,64,125,216,343,512,729,1000,1331,1728,2197,2744,3375,4096,4913,5832,6859,8000,9261]
span (/='i') "this"
("th","is")
break (=='i') "thisis"
("th","isis")
sort [14,3,54]
[3,14,54]
reverse $sort [14,3,54]
[54,14,3]
group ["1","1", "3"]
[["1","1"],["3"]]
zip [1,2,5] [3,4]
[(1,3),(2,4)]
let x=[1,2] in sum x
3
isInfixOf "cat" "catda"
True
"hey" `isPrefixOf` "hey there!"
True
"hey" `isPrefixOf` "f hey there!"
False
"there!" `isSuffixOf` "oh hey there!"
True
"there!" `isSuffixOf` "oh hey there! f"
False
elem 1 [1,2,3]
True
elem 11 [1,2,3]
False
partition (>3) [1,3,5,6,3,2,1,0,3,7]
([5,6,7],[1,3,3,2,1,0,3])
let bign n = if n>0 then True else False
let ds = partition (bign) [-5,1,3,5,6,3,2,1,0,3,7]
ds
([1,3,5,6,3,2,1,3,7],[-5,0])
partition (`elem` "AB") "BOBsidneyMORGANeddy"
("BBA","OsidneyMORGNeddy")
find (=='f') "gasdf"
Just 'f'
find (=='f') "gasdgd"
Nothing
'f' `elem` "gas"
False
elemIndex 11 [1,2,3]
Nothing
elemIndex 1 [1,2,3]
Just 0
elemIndices 1 [1,2,3,1]
[0,3]
findIndices (=='f') "gasdgfdf"
[5,7]
findIndex (=='f') "gasdgfdf"
Just 5
zip [1,2] [3,4,5]
[(1,3),(2,4)]
zip [1,2,3,4,5] [3,4,5]
[(1,3),(2,4),(3,5)]
zip4 [2,3,3] [2,2,2] [5,5,3] [2,2,2]
[(2,2,5,2),(3,2,5,2),(3,2,3,2)]
zipWith (+) [1,2,3] [4,5,2,2]
[5,7,5]
lines "first line\nsecond line\nthird line"
["first line","second line","third line"]
unlines ["first line", "second line", "third line"]
"first line\nsecond line\nthird line\n"
words "first li ne"
["first","li","ne"]
words "first line"
["first","line"]
unwords ["first","li","ne"]
"first li ne"
nub [1,3,2,4,3,2,1,2,3,4,3,2,1]
[1,3,2,4]
nub "Lots of words and stuff"
"Lots fwrdanu"
delete 'h' "hey there ghang!"
"ey there ghang!"
delete 'h' $ delete 'h' $ "hey there ghang!"
[1,2] \\ [2,3,4]
[1]
[2,3,4] \\[1,2]
[3,4]
union [1,2,3] [2,3,4]
[1,2,3,4]
[1,2,3] `intersect` [2,3,4]
[2,3]
insert 4 [15,2,2,3,5,6,7]
[4,15,2,2,3,5,6,7]
insert 4 [2,2,3,5,6,7]
[2,2,3,4,5,6,7]
insert 3 [1,2,4,3,2,1]
[1,2,3,4,3,2,1]
groupBy登场! 它取一个含两个参数的函数作为参数来判定相等性.
let values = [1,2,3,-3,-2,1,2,3,-3,-2]
let compaire2Num x y = if (x*y > 0 ) then True else False
groupBy ( compaire2Num ) values
[[1,2,3],[-3,-2],[1,2,3],[-3,-2]]
groupBy :: (a -> a -> Bool) -> [a] -> [[a]]
functor a,a 返回Bool；
入参为【a】,出差为【【a】】
group [1,1,1,2,2,3]
[[1,1,1],[2,2],[3]]
let sortGT a b = if a< b then GT else LT
sortBy sortGT values
[3,3,2,2,1,1,-2,-2,-3,-3]
let xval = [13,12,3]
sortBy sortGT xval
Data.Char
Prelude Data.List> :m Data.Char
Prelude Data.Char> :t group
Prelude Data.Char> import Data.List
(0.00 secs, 0 bytes)
Prelude Data.Char Data.List>
isControl '、'
False
isSpace ' '
True
isLower 'a'
True
isUpper 'A'
True
isAlpha 'a'
True
isAlpha '4'
False
isAlphaNum '1'
True
isPrint 'f'
True
isDigit '2'
True
isOctDigit '7'
True
isOctDigit '8'
False
isHexDigit 'g'
False
isHexDigit 'e'
True
isLetter '$'
False
isNumber '1'
True
isPunctuation ';'
True
isSymbol '$'
True
isAscii '&'
True
all isLetter "gdff"
True
all isLetter "gd2f"
False
generalCategory 'a'
LowercaseLetter
map generalCategory "f1'$"
[LowercaseLetter,DecimalNumber,OtherPunctuation,CurrencySymbol]
map toUpper "fa2"
"FA2"
map toTitle "gfa das"
"GFA DAS"
digitToInt 'f'
15
intToDigit 15
'f'
ord '%'
37
chr 97
'a'
Prelude Data.Char Data.List> let encode shift msg = map chr $ map (+ shift) ords
Prelude Data.Char Data.List| where ords = map ord msg
Data.Map
Prelude Data.Char Data.List> import
(0.02 secs, 551624 bytes)
Prelude Data.Char Data.List Data.Map>
Prelude.filter odd [2,4,1,3,6,8,5,7]
:t Data.Map.filter
Data.Map.filter :: (a -> Bool) -> Map k a -> Map k a
fromList [("betty","555-2938"),("bonnie","452-2928"),("lucille","205-2928")]
Loading package array-0.4.0.1 ... linking ... done.
Loading package deepseq-1.3.0.1 ... linking ... done.
Loading package containers-0.5.0.0 ... linking ... done.
fromList [("betty","555-2938"),("bonnie","452-2928"),("lucille","205-2928")]
fromList [(1,2),(3,4),(3,2),(5,5)]
fromList [(1,2),(3,2),(5,5)]
去掉重复key的
import qualified Data.Map as Map
Map.insert 3 100 Map.empty
fromList [(3,100)]
Map.insert 5 600 (Map.insert 4 200 ( Map.insert 3 100 Map.empty))
fromList [(3,100),(4,200),(5,600)]
let am = Map.empty
Map.insert 3 100 am
fromList [(3,100)]
Map.null Map.empty
True
let am = Map.fromList [(2,4),(3,3),(4,2),(5,4),(6,4)]
Map.size am
5
Map.singleton 3 9 $ Map.insert 5 9
:368:1:
Couldn't match expected type `(Map k1 a1 -> Map k1 a1) -> t0'
with actual type `Map k0 a0'
The first argument of ($) takes one argument,
but its type `Map k0 a0' has none
In the expression: singleton 3 9 $ Data.Map.insert 5 9
In an equation for `it': it = singleton 3 9 $ Data.Map.insert 5 9
Map.insert 5 9 $ Map.singleton 3 9
fromList [(3,9),(5,9)]
am
fromList [(2,4),(3,3),(4,2),(5,4),(6,4)]
Map.lookup 2 am
Just 4
Map.member 2 am
True
Map.map (*100) am
fromList [(2,400),(3,300),(4,200),(5,400),(6,400)]
Map.map (>0) am
fromList [(2,True),(3,True),(4,True),(5,True),(6,True)]
Map.filter (>3) am
fromList [(2,4),(5,4),(6,4)]
Map.fromListWith max [(2,3),(2,4),(2,1)]
fromList [(2,4)]
Map.fromListWith (+) [(2,3),(2,4),(2,1)]
fromList [(2,8)]
Map.insertWith (+) 3 100 $ Map.fromList [(3,4),(5,103),(6,339)]
fromList [(3,104),(5,103),(6,339)]
Map.insertWith (-) 5 100 $ Map.fromList [(3,4),(5,103),(6,339)]
fromList [(3,4),(5,-3),(6,339)]
Data.Set
import qualified Data.Set as Set
let text1 = "I just had an anime dream,Anime..,Reality..,Are they so different?"
let set1 = Set.fromlist text1
set1
fromList " ,.?AIRadefhijlmnorstuy"
Set.intersection set1 set2
Set.difference set1 set2
Set.union set1 set2
Set.null Set.empty
True
Set.null set1
False
Set.insert 4 $ Set.fromList [9,3,8,1]
fromList [1,3,4,8,9]
Set.delete ' ' $Set.delete 'a' aa
Set.fromList [2,3,4] `Set.isSubsetOf` Set.fromList [1,2,3,4,5]
True
Set.fromList [1,2,3,4,5] `Set.isProperSubsetOf` Set.fromList [1,2,3,4,5]
Set.map (+1) $ Set.fromList [1,2,3,4,5]
Set.filter odd $ Set.fromList [3,4,5,6,7,2,3,4]
:cd d:\haskexam
:load geometry.hs
module Geometry
(
sphereVolume
,sphereArea
,cubeVolume
,cubeArea
,cuboidArea
,cuboidVolume
) where
sphereVolume :: Float -> Float
sphereVolume radius = (4.0 / 3.0) * pi * (radius ^ 3)
data Shape = Circle Float Float Float | Rectangle Float Float Float Float deriving (Show)
let surface (Circle _ _ r) = pi * r ^ 2
surface $ Circle 10 20 10
314.15927
Data.List.map (Circle 10 20) [4,5,6,6]
[Circle 10.0 20.0 4.0,Circle 10.0 20.0 5.0,Circle 10.0 20.0 6.0,Circle 10.0 20.0 6.0]
//取得愿的半径
let radiusCircle (Circle _ _ r) = r
radiusCircle $ Circle 1 1 2
2.0
data Circle = Circle{x::Float,y::Float, radius::Float} deriving (Show)
x $Circle 2 3 4
2.0
data Person = Person {age::Int, name::String} deriving (Show,Eq)
read "1"::Int
1
compare 2 3
LT
compare True False
GT
True > False
True
deriving (Eq, Ord, Show, Read, Bounded, Enum)
小写的不行
data ab = abc| efg
:67:11: Not a data constructor: `abc'
首字母大写ok.
data AB = ABS| EFG
data AB = ABS | EFG
它也是Enmu的实例，可以得到前一天和后一天，并且可以对此使用List的区间。
ghci> succ Monday
Tuesday
ghci> pred Saturday
Friday
x<-getLine
foldr (*)3 [1 ,2,3]
18
