github/semantic
1
1
Fork 0
mirror of https://github.com/github/semantic.git synced 2024-11-28 10:15:55 +03:00
Code Issues Projects Releases Wiki Activity

Use fromMaybe to unpack with a default value.

Browse Source 
I was looking for exactly this! Very nice.
This commit is contained in:
Rob Rix 2015-11-27 09:53:37 -05:00
parent 982fe363d8
commit fe07b475e4
1 changed files with 2 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
src/Interpreter.hs
View File

@ -10,6 +10,7 @@ import Term
import Control.Monad.Free
import Control.Comonad.Cofree
import Data.Map
import Data.Maybe
hylo :: Functor f => (t -> f b -> b) -> (a -> (t, f a)) -> a -> b
hylo down up a = down annotation $ hylo down up <$> syntax where
@ -55,6 +56,4 @@ run comparable (Free (ByIndex a b f)) = run comparable . f $ ses (constructAndRu
type Comparable a annotation = Term a annotation -> Term a annotation -> Bool
interpret :: (Eq a, Eq annotation) => Comparable a annotation -> Term a annotation -> Term a annotation -> Diff a annotation
interpret comparable a b = maybeReplace $ constructAndRun comparable a b where
maybeReplace (Just a) = a
maybeReplace Nothing = Pure $ Replace a b
interpret comparable a b = fromMaybe (Pure $ Replace a b) $ constructAndRun comparable a b