foldl package:containers

Fold the values in the map using the given left-associative binary operator, such that foldl f z == foldl f z . elems. For example,

elems = reverse . foldl (flip (:)) []

let f len a = len + (length a)
foldl f 0 (fromList [(5,"a"), (3,"bbb")]) == 4

Fold the elements in the set using the given left-associative binary operator, such that foldl f z == foldl f z . toAscList. For example,

toDescList set = foldl (flip (:)) [] set

Fold the values in the map using the given left-associative binary operator, such that foldl f z == foldl f z . elems. For example,

elems = reverse . foldl (flip (:)) []

let f len a = len + (length a)
foldl f 0 (fromList [(5,"a"), (3,"bbb")]) == 4

Fold the elements in the set using the given left-associative binary operator, such that foldl f z == foldl f z . toAscList. For example,

toDescList set = foldl (flip (:)) [] set

A strict version of foldl. Each application of the operator is evaluated before using the result in the next application. This function is strict in the starting value.

Fold the keys and values in the map using the given left-associative binary operator, such that foldlWithKey f z == foldl (\z' (kx, x) -> f z' kx x) z . toAscList. For example,

keys = reverse . foldlWithKey (\ks k x -> k:ks) []

let f result k a = result ++ "(" ++ (show k) ++ ":" ++ a ++ ")"
foldlWithKey f "Map: " (fromList [(5,"a"), (3,"b")]) == "Map: (3:b)(5:a)"

A strict version of foldlWithKey. Each application of the operator is evaluated before using the result in the next application. This function is strict in the starting value.

A strict version of foldl. Each application of the operator is evaluated before using the result in the next application. This function is strict in the starting value.

A strict version of foldl. Each application of the operator is evaluated before using the result in the next application. This function is strict in the starting value.

Fold the keys and values in the map using the given left-associative binary operator, such that foldlWithKey f z == foldl (\z' (kx, x) -> f z' kx x) z . toAscList. For example,

keys = reverse . foldlWithKey (\ks k x -> k:ks) []

let f result k a = result ++ "(" ++ (show k) ++ ":" ++ a ++ ")"
foldlWithKey f "Map: " (fromList [(5,"a"), (3,"b")]) == "Map: (3:b)(5:a)"

A strict version of foldlWithKey. Each application of the operator is evaluated before using the result in the next application. This function is strict in the starting value.

foldlWithIndex is a version of foldl that also provides access to the index of each element.

A strict version of foldl. Each application of the operator is evaluated before using the result in the next application. This function is strict in the starting value.

unfoldl f x is equivalent to reverse (unfoldr (fmap swap . f) x).