lib.lists.foldr

“right fold” a binary function op between successive elements of list with nul as the starting value, i.e., foldr op nul [x_1 x_2 ... x_n] == op x_1 (op x_2 ... (op x_n nul)).

Inputs

op

1. Function argument

nul

2. Function argument

list

3. Function argument

Type

foldr :: (a -> b -> b) -> b -> [a] -> b

Examples

concat = foldr (a: b: a + b) "z"
concat [ "a" "b" "c" ]
=> "abcz"
# different types
strange = foldr (int: str: toString (int + 1) + str) "a"
strange [ 1 2 3 4 ]
=> "2345a"

Noogle detected

• lib.fold
• lib.foldr
• lib.lists.fold

foldr = op: nul: list:
    let
      len = length list;
      fold' = n:
        if n == len
        then nul
        else op (elemAt list n) (fold' (n + 1));
    in fold' 0;