Ascend FD-23R Manual do Utilizador descarregar pdf (Página 77)

scanr F Q0 [X|Xs] = auxForScanr F X (scanr F Q0 Xs)

%where

auxForScanr F X Ys = [F X (head Ys)|Ys]

scanr1 :: (A -> A -> A) -> [A] -> [A]

scanr1 F [X] = [X]

scanr1 F [X,Y|Xs] = auxForScanr F X (scanr1 F [Y|Xs])

%% List breaking functions:

%% take n Xs returns the first n elements of Xs

%% drop n Xs returns the remaining elements of Xs

%% splitAt n Xs = (take n Xs , drop n Xs )

%% takeWhile P Xs returns the longest initial segment of Xs whose

%% elements satisfy p

%% dropWhile P Xs returns the remaining portion of the list

%% span P Xs = (takeWhile P Xs , dropWhile P Xs )

%% takeUntil P Xs returns the list of elements upto and including the

%% first element of Xs which satisfies p

take :: int -> [A] -> [A]

take N [] = []

take N [X|Xs] = if N==0 then [] else [X|take (N-1) Xs]

drop :: int -> [A] -> [A]

drop N [] = []

drop N [X|Xs] = if N==0 then [X|Xs] else drop (N-1) Xs

splitAt :: int -> [A] -> ( [A] , [A] )

splitAt N [] = ([],[])

splitAt N [X|Xs] = if N==0

then ([], [X|Xs])

else auxForSplitAt X (splitAt (N-1) Xs)

%where

auxForSplitAt X (Xs,Ys) = ([X|Xs],Ys)

takeWhile :: (A -> bool) -> [A] -> [A]

takeWhile P [] = []

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Ascend FD-23R Manual do Utilizador Página 77