foldl package:ghc

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

Strict left fold.

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.

Monadic version of foldl that discards its result