Functii din Prelude, A-F
From HaskellWiki
Lista de functii des folosite, cu nume de la A la F.
Pentru a vedea un exemplu de folosire (si tipul fiecarei functii) cautati numele ei mai jos pe pagina, cu Find-ul browser-ului.
abs - valoarea absoluta
all - predicatul e adevarat pe toata lista de argumente ?
and - conjunctie generalizata pe o lista de valori de tip Bool
any - exista o valoare pe lista care satisface predicatul (in engleza aceste intrebari se pun cu any)
atan - arctangenta
break - rupe o lista inaintea locului/elementului care satisface un predicat
ceiling - rotunjirea superioara la un intreg
chr - caracterul cu acel cod ascii, conversie numar - caracter
concat - concatenarea unui grup de liste , dat ca lista :) de liste
cos - cosinusul
digitToInt - transforma caracterul (daca e cifra) cifra in valoarea lui
div - impartirea intreaga
drop - arunca primele dintr-o lista
dropWhile - arunca primele care indeplinesc conditia
-- folositor la a ajunge la primele elemente semnificative daca pui conditia invers
elem - apartine listei
error - genereaza eroare si poate avea orice tip, folositi-o deci oriunde exp - e(x)
flip - schimba ordinea argumentelor unei functii cu doua arg
filter - alege ce satisface predicatul, din lista data
:t abs abs :: Num a => a -> a Prelude> abs -9 ERROR - Illegal Haskell 98 class constraint in inferred type *** Expression : abs - 9 *** Type : (Num a, Num (a -> a)) => a -> a Prelude> abs (-9) 9 Prelude> abs (-9.3) 9.3 Prelude> ---- Prelude> :t all all :: (a -> Bool) -> [a] -> Bool Prelude> all isDigit "12234678" True Prelude> all isDigit "danu" False Prelude> ---- lse Prelude> :t and and :: [Bool] -> Bool Prelude> and [True,True ,True] True Prelude> and [True,True ,True,False] False Prelude> ---- Prelude> :t atan atan :: Floating a => a -> a Prelude> Prelude> 4 * atan 1 3.14159 ---- relude> :t break break :: (a -> Bool) -> [a] -> ([a],[a]) Prelude> break isDigit "R2D2" ("R","2D2") Prelude> break isDigit "3PO" ("","3PO") Prelude> Prelude> break isSpace "La Multi Ani 2008!" ("La"," Multi Ani 2008!") Prelude> Prelude> break (==0) [5,24,23,2,1,0,-1] ([5,24,23,2,1],[0,-1]) Prelude> ---- Prelude> :t ceiling ceiling :: (RealFrac a, Integral b) => a -> b Prelude> ceiling 2.2 3 Prelude> ceiling 1.242 2 Prelude> ceiling 1.42 2 Prelude> ---- Prelude> :t chr chr :: Int -> Char Prelude> chr 66 'B' Prelude> chr 65 'A' Prelude> chr 32 ' ' Prelude> ---- Prelude> :t concat concat :: [[a]] -> [a] Prelude> concat ["La", "Multi", "Ani","!"] "LaMultiAni!" Prelude> ---- Prelude> :t cos cos :: Floating a => a -> a Prelude> cos 0 1.0 Prelude> ---- relude> digitToInt "0" ERROR - Type error in application *** Expression : digitToInt "0" *** Term : "0" *** Type : String *** Does not match : Char Prelude> digitToInt '0' 0 Prelude> digitToInt '1' 1 Prelude> digitToInt '2' 2 Prelude> digitToInt '3' 3 Prelude> digitToInt '4' 4 Prelude> digitToInt 'u' Program error: Char.digitToInt: not a digit Prelude> ---- Prelude> :t div div :: Integral a => a -> a -> a Prelude> 10 `div` 3 3 Prelude> ---- Prelude> :t drop drop :: Int -> [a] -> [a] Prelude> drop 2 ["La", "Multi", "Ani","!"] ["Ani","!"] Prelude> ----- Prelude> :t dropWhile dropWhile :: (a -> Bool) -> [a] -> [a] Prelude> dropWhile (==0) [0,0,0,0,1,2,3,4,0,0,1,2] [1,2,3,4,0,0,1,2] Prelude> Prelude> :t elem elem :: Eq a => a -> [a] -> Bool Prelude> elem "!" ["La", "Multi", "Ani","!"] True Prelude> elem "2008" ["La", "Multi", "Ani","!"] False Prelude> elem "2000" ["La", "Multi", "Ani","!"] False Prelude> ---- Prelude> :t error error :: String -> a Prelude> error "Stop the train!" ERROR - Cannot find "show" function for: *** Expression : error "Stop the train!" *** Of type : a Prelude> error "Stop the train!" :Char ERROR - Undefined constructor function "Char" Prelude> error "Stop the train!" :: String " Program error: Stop the train! Prelude> ---- Prelude> :t exp exp :: Floating a => a -> a Prelude> exp 1 2.71828 Prelude> ---- Prelude> :t flip flip :: (a -> b -> c) -> b -> a -> c Prelude> (flip (>)) 1 2 True Prelude> ---- Prelude> :t filter filter :: (a -> Bool) -> [a] -> [a] Prelude> filter (>2) [1,2,3,4,1] [3,4] Prelude>
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