Functional programming 是否有更好的方法在Idris中编写嵌套案例?
以下是Edwin书中的一段Idris代码:Functional programming 是否有更好的方法在Idris中编写嵌套案例?,functional-programming,idris,Functional Programming,Idris,以下是Edwin书中的一段Idris代码: data DataStore : Type where MkData : (size : Nat) -> (items : Vect size String) -> DataStore proccessInput : DataStore -> String -> Maybe (String, DataStore) proccessInput store@(MkData size
data DataStore : Type where
MkData : (size : Nat) ->
(items : Vect size String) ->
DataStore
proccessInput : DataStore -> String -> Maybe (String, DataStore)
proccessInput store@(MkData size items) input =
case map trim $ span (/= ' ') input of
("add", item) => Just ("ID " ++ show size ++ "\n", MkData _ (item :: items))
("get", val) => case all isDigit (unpack val) of
False => Just ("Invalid command\n", store)
True => case integerToFin (cast val) size of
Nothing => Just ("Out of range\n", store)
(Just id) => Just (index id items ++ " \n", store)
("quit", "") => Nothing
(_, _) => Just ("Invalid command\n", store)
我已经消除了一些我认为是多余的代码(一些助手函数),但我仍然发现这些代码有些多余。我认为大小写拆分非常难看。模式匹配绑定是一种方便的符号,用于处理可能失败的操作序列,这可能有助于减少嵌套大小写块的最近性