mirror of
https://github.com/idris-lang/Idris2.git
synced 2024-12-30 07:02:24 +03:00
27 lines
703 B
Idris
27 lines
703 B
Idris
|
module RLE
|
||
|
|
|
||
|
|
import Data.List
|
||
|
|
import Data.Singleton
|
||
|
|
import Decidable.Equality
|
||
|
|
|
||
|
|
%default total
|
||
|
|
|
||
|
|
data RunLength : List a -> Type where
|
||
|
|
Empty : RunLength []
|
||
|
|
Run : (n : Nat)
|
||
|
|
-> (x : a)
|
||
|
|
-> (rest : RunLength more)
|
||
|
|
-> RunLength (replicate n x ++ more)
|
||
|
|
|
||
|
|
uncompress : RunLength xs -> Singleton xs
|
||
|
|
uncompress Empty = [| [] |]
|
||
|
|
uncompress (Run n x comp) = [| (pure $ replicate n x) ++ uncompress comp |]
|
||
|
|
|
||
|
|
rle : DecEq a => (xs : List a) -> RunLength xs
|
||
|
|
rle [] = Empty
|
||
|
|
rle (x :: xs) with (rle xs)
|
||
|
|
rle (x :: []) | Empty = Run 1 x Empty
|
||
|
|
rle (x :: (replicate n y ++ more)) | (Run n y rest) = case decEq x y of
|
||
|
|
Yes Refl => Run (S n) y rest
|
||
|
|
No contra => Run 1 x (Run n y rest)
|