Lists

Lists are used to store multiple values of the same type.

List Operations

这些操作并不修改原列表的值，返回的是其 copy.

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head :: [a] -> a            -- returns the first element
last :: [a] -> a            -- returns the last element
tail :: [a] -> [a]          -- returns everything except the first element
init :: [a] -> [a]          -- returns everything except the last element
take :: Int -> [a] -> [a]   -- returns the n first elements
drop :: Int -> [a] -> [a]   -- returns everything except the n first elements
(++) :: [a] -> [a] -> [a]   -- lists are catenated with the ++ operator
(!!) :: [a] -> Int -> a     -- lists are indexed with the !! operator
reverse :: [a] -> [a]       -- reverse a list
null :: [a] -> Bool         -- is this list empty?
length :: [a] -> Int        -- the length of a list

Maybe Type

约等于 Rust 里的 Option<T>

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Maybe Int
-- <=>
Nothing, Just 0, Just 114514, ...

Either Type

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Either String Int
-- <=>
Left "asdf", Right 1, Right 67, Left "qweohuff 0", ...
Data and Types
License

本文采用 署名-非商业性使用-相同方式共享 4.0 国际 许可协议，转载请注明出处。