scanr -package:vector-sized

scanr is the right-to-left dual of scanl. Note that the order of parameters on the accumulating function are reversed compared to scanl. Also note that

head (scanr f z xs) == foldr f z xs.

Examples

>>> scanr (+) 0 [1..4]
[10,9,7,4,0]

>>> scanr (+) 42 []
[42]

>>> scanr (-) 100 [1..4]
[98,-97,99,-96,100]

>>> scanr (\nextChar reversedString -> nextChar : reversedString) "foo" ['a', 'b', 'c', 'd']
["abcdfoo","bcdfoo","cdfoo","dfoo","foo"]

>>> force $ scanr (+) 0 [1..]
*** Exception: stack overflow

scanr is the right-to-left dual of scanl. Note that

head (scanr f z xs) == foldr f z xs.

scanr is similar to foldr, but returns a list of successive reduced values from the right.

scanr f z [..., x{n-1}, xn] == [..., x{n-1} `f` (xn `f` z), xn `f` z, z]

Note that

head (scanr f z xs) == foldr f z xs
last (scanr f z xs) == z

scanr is the right-to-left dual of scanl.

scanr is similar to foldr, but returns a list of successive reduced values from the right.

scanr f z [..., x{n-1}, xn] == [..., x{n-1} `f` (xn `f` z), xn `f` z, z]

Note that

head (scanr f z xs) == foldr f z xs
last (scanr f z xs) == z

O(n) scanr is the right-to-left dual of scanl. Performs replacement on invalid scalar values.

scanr f v == reverse . scanl (flip f) v . reverse

scanr is the right-to-left dual of scanl.

O(n) Right-to-left scan.

O(n) Right-to-left scan.

O(n) Right-to-left scan.

O(n) Right-to-left scan.

O(n) Right-to-left scan.

scanr is the right-to-left dual of scanl. Note that the order of parameters on the accumulating function are reversed compared to scanl. Also note that

head (scanr f z xs) == foldr f z xs.

>>> scanr (+) 0 [1..4]
[10,9,7,4,0]

>>> scanr (+) 42 []
[42]

>>> scanr (-) 100 [1..4]
[98,-97,99,-96,100]

>>> scanr (\nextChar reversedString -> nextChar : reversedString) "foo" ['a', 'b', 'c', 'd']
["abcdfoo","bcdfoo","cdfoo","dfoo","foo"]

>>> force $ scanr (+) 0 [1..]
*** Exception: stack overflow

Like scan but start scanning from the right

O(n) scanr is the right-to-left dual of scanl. Performs replacement on invalid scalar values.

scanr f v == reverse . scanl (flip f) v . reverse

scanr is the right-to-left dual of scanl. Note that

head (scanr f z xs) == foldr f z xs.

Equivalent to scanr from Data.List when applied to a String, but preserves all non-character data.

scanr is the right-to-left dual of scanl.

Use a lazy right Scanr to transform a stream. The following example extracts the input stream up to a point where the running average of elements is no more than 10:

>>> import Data.Maybe (fromJust)

>>> let avg = Scanr.teeWith (/) Scanr.sum (fmap fromIntegral Scanr.length)

>>> s = Stream.enumerateFromTo 1.0 100.0

>>> :{
Stream.fold Fold.toList
$ fmap fst
$ Stream.takeWhile (\(_,x) -> x <= 10)
$ Stream.scanr (Scanr.tee Scanr.identity avg) s
:}
[1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0,13.0,14.0,15.0,16.0,17.0,18.0,19.0]