Difference between revisions of "Functii din Prelude, A-F"

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[[Category:Ro]]
 
[[Image:Haskelllogo-small-flag-RO-8.jpg|center|Haskell - Un limbaj functional pur]]
 
 
 
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
 
 
----
 
<haskell>
 
: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>
 
 
</haskell>
 
 
----
 
Pagina indexata la indexul [[Category:Ro]] [http://www.haskell.org/haskellwiki/Category:Ro Categories:Ro]
 
----
 
[http://www.haskell.org/haskellwiki/Ro/Haskell <= Inapoi la pagina principala Ro/Haskell. ]<br> <br>
 
[http://www.haskell.org/haskellwiki/Intrebarile_incepatorului <'''-''' Inapoi la Intrebarile incepatorului Ro/Haskell. ]
 

Revision as of 14:58, 6 February 2021