mirror of
https://github.com/correl/elm.git
synced 2024-11-17 03:00:06 +00:00
59 lines
965 B
Text
59 lines
965 B
Text
module ListOps exposing (..)
|
|
|
|
|
|
length : List a -> Int
|
|
length list =
|
|
foldl (\_ acc -> 1 + acc) 0 list
|
|
|
|
|
|
reverse : List a -> List a
|
|
reverse list =
|
|
foldl (::) [] list
|
|
|
|
|
|
foldl : (a -> b -> b) -> b -> List a -> b
|
|
foldl f acc list =
|
|
case list of
|
|
[] ->
|
|
acc
|
|
|
|
head :: tail ->
|
|
foldl f (f head acc) tail
|
|
|
|
|
|
foldr : (a -> b -> b) -> b -> List a -> b
|
|
foldr f acc list =
|
|
case list of
|
|
[] ->
|
|
acc
|
|
|
|
head :: tail ->
|
|
f head (foldr f acc tail)
|
|
|
|
|
|
map : (a -> b) -> List a -> List b
|
|
map f list =
|
|
foldr (\x acc -> f x :: acc) [] list
|
|
|
|
|
|
filter : (a -> Bool) -> List a -> List a
|
|
filter f list =
|
|
foldr
|
|
(\x acc ->
|
|
if f x then
|
|
x :: acc
|
|
else
|
|
acc
|
|
)
|
|
[]
|
|
list
|
|
|
|
|
|
append : List a -> List a -> List a
|
|
append xs ys =
|
|
foldr (::) ys xs
|
|
|
|
|
|
concat : List (List a) -> List a
|
|
concat list =
|
|
foldr append [] list
|