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mirror of https://github.com/idris-lang/Idris2.git synced 2024-12-23 19:54:50 +03:00
Idris2/samples/With.idr
2021-01-21 11:33:03 +00:00

47 lines
1.5 KiB
Idris

import Data.Vect
import Data.Nat
my_filter : (a -> Bool) -> Vect n a -> (p ** Vect p a)
my_filter p [] = ( _ ** [] )
my_filter p (x :: xs) with (filter p xs)
my_filter p (x :: xs) | ( _ ** xs' ) = if (p x) then ( _ ** x :: xs' ) else ( _ ** xs' )
foo : Int -> Int -> Bool
foo n m with (n + 1)
foo _ m | 2 with (m + 1)
foo _ _ | 2 | 3 = True
foo _ _ | 2 | _ = False
foo _ _ | _ = False
data Parity : Nat -> Type where
Even : {n : _} -> Parity (n + n)
Odd : {n : _} ->Parity (S (n + n))
-- parity : (n : Nat) -> Parity n
-- parity Z = Even {n = Z}
-- parity (S Z) = Odd {n = Z}
-- parity (S (S k)) with (parity k)
-- parity (S (S (j + j))) | Even
-- = rewrite plusSuccRightSucc j j in Even {n = S j}
-- parity (S (S (S (j + j)))) | Odd
-- = rewrite plusSuccRightSucc j j in Odd {n = S j}
helpEven : (j : Nat) -> Parity (S j + S j) -> Parity (S (S (plus j j)))
helpEven j p = rewrite plusSuccRightSucc j j in p
helpOdd : (j : Nat) -> Parity (S (S (j + S j))) -> Parity (S (S (S (j + j))))
helpOdd j p = rewrite plusSuccRightSucc j j in p
parity : (n:Nat) -> Parity n
parity Z = Even {n=Z}
parity (S Z) = Odd {n=Z}
parity (S (S k)) with (parity k)
parity (S (S (j + j))) | Even = helpEven j (Even {n = S j})
parity (S (S (S (j + j)))) | Odd = helpOdd j (Odd {n = S j})
natToBin : Nat -> List Bool
natToBin Z = Nil
natToBin k with (parity k)
natToBin (j + j) | Even = False :: natToBin j
natToBin (S (j + j)) | Odd = True :: natToBin j