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They can be imported from the modules Data.Fin, Data.Vect, and Data.So respectively. The general thinking here is that not every program is going to need these, and they are often used especially by newcomers in place of something more appropriate. Also, all of them are useful for teaching, which means it is instructive for tutorials to introduce them and have people implement them themselves.
35 lines
1017 B
Idris
35 lines
1017 B
Idris
module Main
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import Data.Vect
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data RLE : Vect n Char -> Type where
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REnd : RLE []
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RChar : {xs : Vect k Char} ->
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(n : Nat) -> (c : Char) -> (rs : RLE xs) ->
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RLE (replicate (S n) c ++ xs)
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------------
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rle : (xs : Vect n Char) -> RLE xs
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rle [] = REnd
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rle (x :: xs) with (rle xs)
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rle (x :: []) | REnd = RChar 0 x REnd
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rle (x :: (c :: (replicate n c ++ ys))) | (RChar n c rs) with (decEq x c)
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rle (x :: (x :: (replicate n x ++ ys))) | (RChar n x rs) | (Yes Refl)
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= RChar (S n) x rs
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rle (x :: (c :: (replicate n c ++ ys))) | (RChar n c rs) | (No f)
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= RChar 0 x (RChar n c rs)
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compress : Vect n Char -> String
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compress xs with (rle xs)
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compress [] | REnd = ""
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compress (c :: (replicate n c ++ xs1)) | (RChar n c rs)
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= show (the Integer (cast (S n))) ++
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strCons c (compress xs1)
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compressString : String -> String
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compressString xs = compress (fromList (unpack xs))
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main : IO ()
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main = putStrLn (compressString "foooobaaaarbaaaz")
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