feat: add MonadAsk & MonadReader instances (#208)

* feat: add MonadAsk & MonadReader instances

* Update CHANGELOG.md

* Update src/Parsing.purs

Co-authored-by: Nathan Faubion <[email protected]>

* Update src/Parsing.purs

Co-authored-by: James Brock <[email protected]>

* fix: remove unnecessary constraint

Co-authored-by: Nathan Faubion <[email protected]>
Co-authored-by: James Brock <[email protected]>

Author: 3 people

CHANGELOG.md

@@ -10,6 +10,8 @@ Breaking changes:
 
 New features:
 
+- add `MonadAsk` and `MonadReader` instances (#208 by @bentongxyz)
+
 Other improvements:
 
 ## [v10.0.0](https://github.com/purescript-contrib/purescript-parsing/releases/tag/v9.1.0) - 2022-07-18

src/Parsing.purs

@@ -33,6 +33,7 @@ import Control.Alt (class Alt)
 import Control.Apply (lift2)
 import Control.Lazy (class Lazy)
 import Control.Monad.Error.Class (class MonadError, class MonadThrow, catchError, throwError)
+import Control.Monad.Reader.Class (class MonadAsk, class MonadReader, ask, local)
 import Control.Monad.Rec.Class (class MonadRec, Step(..), tailRecM)
 import Control.Monad.State.Class (class MonadState, state)
 import Control.Monad.Trans.Class (class MonadTrans, lift)
@@ -278,6 +279,15 @@ instance MonadRec (ParserT s m) where
 instance (MonadState t m) => MonadState t (ParserT s m) where
   state k = lift (state k)
 
+instance (MonadAsk r m) => MonadAsk r (ParserT s m) where
+  ask = lift ask
+
+instance (MonadReader r m) => MonadReader r (ParserT s m) where
+  local f (ParserT k) = ParserT
+    ( mkFn5 \state1 more lift throw done ->
+        runFn5 k state1 more (lift <<< local f) throw done
+    )
+
 instance MonadThrow ParseError (ParserT s m) where
   throwError err = ParserT
     ( mkFn5 \state1 _ _ throw _ ->