Merge pull request #120 from martijnbastiaan/readMaybeEither

Banish `String` on `readMaybe` and `readEither`

ChangeLog.md

@@ -1,3 +1,8 @@
+Unreleased
+=====
+
+* Banish `String` on `readMaybe` and `readEither`.
+
 0.3.0
 =====
 

export_lists/protolude-10.exports

@@ -750,10 +750,10 @@ ratioPrec from GHC.Real
 ratioPrec1 from GHC.Real
 ratioZeroDenominatorError from GHC.Real
 readChan from Control.Concurrent.Chan
-readEither from Text.Read
+readEither from Protolude
 readFile from Data.Text.IO
 readMVar from GHC.MVar
-readMaybe from Text.Read
+readMaybe from Protolude
 reader from Control.Monad.Reader.Class
 reads from Text.Read
 realPart from Data.Complex

export_lists/protolude-11.exports

@@ -750,10 +750,10 @@ ratioPrec from GHC.Real
 ratioPrec1 from GHC.Real
 ratioZeroDenominatorError from GHC.Real
 readChan from Control.Concurrent.Chan
-readEither from Text.Read
+readEither from Protolude
 readFile from Data.Text.IO
 readMVar from GHC.MVar
-readMaybe from Text.Read
+readMaybe from Protolude
 reader from Control.Monad.Reader.Class
 reads from Text.Read
 realPart from Data.Complex

export_lists/protolude-12.exports

@@ -749,10 +749,10 @@ ratioPrec from GHC.Real
 ratioPrec1 from GHC.Real
 ratioZeroDenominatorError from GHC.Real
 readChan from Control.Concurrent.Chan
-readEither from Text.Read
+readEither from Protolude
 readFile from Data.Text.IO
 readMVar from GHC.MVar
-readMaybe from Text.Read
+readMaybe from Protolude
 reader from Control.Monad.Reader.Class
 reads from Text.Read
 realPart from Data.Complex

export_lists/protolude-13.exports

@@ -749,10 +749,10 @@ ratioPrec from GHC.Real
 ratioPrec1 from GHC.Real
 ratioZeroDenominatorError from GHC.Real
 readChan from Control.Concurrent.Chan
-readEither from Text.Read
+readEither from Protolude
 readFile from Data.Text.IO
 readMVar from GHC.MVar
-readMaybe from Text.Read
+readMaybe from Protolude
 reader from Control.Monad.Reader.Class
 reads from Text.Read
 realPart from Data.Complex

export_lists/protolude-14.exports

@@ -749,10 +749,10 @@ ratioPrec from GHC.Real
 ratioPrec1 from GHC.Real
 ratioZeroDenominatorError from GHC.Real
 readChan from Control.Concurrent.Chan
-readEither from Text.Read
+readEither from Protolude
 readFile from Data.Text.IO
 readMVar from GHC.MVar
-readMaybe from Text.Read
+readMaybe from Protolude
 reader from Control.Monad.Reader.Class
 reads from Text.Read
 realPart from Data.Complex

export_lists/protolude-7.exports

@@ -746,10 +746,10 @@ ratioPrec from GHC.Real
 ratioPrec1 from GHC.Real
 ratioZeroDenominatorError from GHC.Real
 readChan from Control.Concurrent.Chan
-readEither from Text.Read
+readEither from Protolude
 readFile from Data.Text.IO
 readMVar from GHC.MVar
-readMaybe from Text.Read
+readMaybe from Protolude
 reader from Control.Monad.Reader.Class
 reads from Text.Read
 realPart from Data.Complex

export_lists/protolude-8.exports

@@ -746,10 +746,10 @@ ratioPrec from GHC.Real
 ratioPrec1 from GHC.Real
 ratioZeroDenominatorError from GHC.Real
 readChan from Control.Concurrent.Chan
-readEither from Text.Read
+readEither from Protolude
 readFile from Data.Text.IO
 readMVar from GHC.MVar
-readMaybe from Text.Read
+readMaybe from Protolude
 reader from Control.Monad.Reader.Class
 reads from Text.Read
 realPart from Data.Complex

export_lists/protolude-9.exports

@@ -746,10 +746,10 @@ ratioPrec from GHC.Real
 ratioPrec1 from GHC.Real
 ratioZeroDenominatorError from GHC.Real
 readChan from Control.Concurrent.Chan
-readEither from Text.Read
+readEither from Protolude
 readFile from Data.Text.IO
 readMVar from GHC.MVar
-readMaybe from Text.Read
+readMaybe from Protolude
 reader from Control.Monad.Reader.Class
 reads from Text.Read
 realPart from Data.Complex

src/Protolude.hs

@@ -128,6 +128,8 @@ module Protolude (
 
   -- * Read functions
   module Read,
+  readMaybe,
+  readEither,
 
   -- * System functions
   module System,
@@ -909,11 +911,10 @@ import Foreign.Storable as Foreign (Storable)
 import Foreign.StablePtr as Foreign (StablePtr)
 
 -- Read instances hiding unsafe builtins (read)
+import qualified Text.Read as Read
 import Text.Read as Read (
     Read
   , reads
-  , readMaybe
-  , readEither
   )
 
 -- Type synonymss for lazy texts
@@ -950,6 +951,29 @@ unsnoc = Foldable.foldr go Nothing
 applyN :: Int -> (a -> a) -> a -> a
 applyN n f = Foldable.foldr (.) identity (List.replicate n f)
 
+-- | Parse a string using the 'Read' instance.
+-- Succeeds if there is exactly one valid result.
+--
+-- >>> readMaybe ("123" :: Text) :: Maybe Int
+-- Just 123
+--
+-- >>> readMaybe ("hello" :: Text) :: Maybe Int
+-- Nothing
+readMaybe :: (Read b, Conv.StringConv a String) => a -> Maybe b
+readMaybe = Read.readMaybe . Conv.toS
+
+-- | Parse a string using the 'Read' instance.
+-- Succeeds if there is exactly one valid result.
+-- A 'Left' value indicates a parse error.
+--
+-- >>> readEither "123" :: Either Text Int
+-- Right 123
+--
+-- >>> readEither "hello" :: Either Text Int
+-- Left "Prelude.read: no parse"
+readEither :: (Read a, Conv.StringConv String e, Conv.StringConv e String) => e -> Either e a
+readEither = first Conv.toS . Read.readEither . Conv.toS
+
 -- | The print function outputs a value of any printable type to the standard
 -- output device. Printable types are those that are instances of class Show;
 -- print converts values to strings for output using the show operation and adds