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https://github.com/Noratrieb/idris-learning.git
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56 lines
2 KiB
Idris
56 lines
2 KiB
Idris
module Main
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import Data.Vect
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data DataStore : Type where
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MkData : (size : Nat) -> (items : Vect size String) -> DataStore
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size : DataStore -> Nat
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size (MkData size items) = size
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items : (store : DataStore) -> Vect (size store) String
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items (MkData size items) = items
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addToStore : DataStore -> String -> DataStore
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addToStore (MkData size items) newitem = MkData _ (addToData items)
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where
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addToData : Vect old String -> Vect (S old) String
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addToData [] = [newitem]
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addToData (x :: xs) = x :: addToData xs
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data Command = Add String
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| Get Integer
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| Quit
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parseCommand : (cmd : String) -> (args : String) -> Maybe Command
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parseCommand "add" args = Just (Add args)
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parseCommand "get" val = case all isDigit (unpack val) of
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True => Just (Get (cast val))
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False => Nothing
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parseCommand "quit" args = Just Quit
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parseCommand _ _ = Nothing
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parse : (input : String) -> Maybe Command
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parse input = case span (/= ' ') input of
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(cmd, args) => parseCommand cmd (ltrim args)
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getEntry : (pos : Integer) -> (store : DataStore) -> Maybe (String, DataStore)
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getEntry pos store = let store_items = items store in
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case integerToFin pos (size store) of
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Nothing => Just ("Out of range\n", store)
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Just idx => Just (index idx store_items ++ "\n", store)
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processInput : DataStore -> String -> Maybe (String, DataStore)
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processInput store inp = case parse inp of
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Nothing => Just ("invalid command\n", store)
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(Just (Add item)) =>
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Just ("ID " ++ show (size store) ++ "\n", addToStore store item)
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(Just (Get pos)) => getEntry pos store
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(Just Quit) => Nothing
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main : IO ()
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main = replWith (MkData _ []) "Command: " processInput
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