mirror of
https://github.com/idris-lang/Idris2.git
synced 2024-12-21 10:41:59 +03:00
27 lines
577 B
Idris
27 lines
577 B
Idris
|
import Data.List.Lazy
|
||
|
|
|
||
|
|
import Debug.Trace
|
||
|
|
|
||
|
|
%default total
|
||
|
|
|
||
|
|
xs : LazyList Nat
|
||
|
|
xs = iterateN 5 (traceValBy (("xs: " ++) . show) . S) Z
|
||
|
|
|
||
|
|
ys : Maybe (List Nat)
|
||
|
|
ys = for xs $ \n => if n >= 3 then Nothing else Just (10 * n)
|
||
|
|
|
||
|
|
xs' : LazyList Nat
|
||
|
|
xs' = iterateN 5 (traceValBy (("xs': " ++) . show) . S) Z
|
||
|
|
|
||
|
|
for' : Monad f => LazyList a -> (a -> f b) -> f $ List b
|
||
|
|
for' [] _ = pure []
|
||
|
|
for' (x::xs) g = pure $ !(g x) :: !(for' xs g)
|
||
|
|
|
||
|
|
ys' : Maybe (List Nat)
|
||
|
|
ys' = for' xs' $ \n => if n >= 3 then Nothing else Just (10 * n)
|
||
|
|
|
||
|
|
main : IO ()
|
||
|
|
main = do
|
||
|
|
putStrLn $ show ys
|
||
|
|
putStrLn $ show ys'
|