Merge pull request #11 from ryanartecona/notFollowedBy

Add `notFollowedBy` combinator

Author: jdegoes

docs/Module.md

@@ -89,6 +89,8 @@
 
     manyTill :: forall s a m e. (Monad m) => ParserT s m a -> ParserT s m e -> ParserT s m [a]
 
+    notFollowedBy :: forall s a m. (Monad m) => ParserT s m a -> ParserT s m Unit
+
     option :: forall m s a. (Monad m) => a -> ParserT s m a -> ParserT s m a
 
     optionMaybe :: forall m s a. (Functor m, Monad m) => ParserT s m a -> ParserT s m (Maybe a)

src/Text/Parsing/Parser/Combinators.purs

@@ -7,6 +7,7 @@ import Data.Either
 
 import Control.Alt
 import Control.Alternative
+import Control.Apply
 import Control.Lazy
 import Control.Monad
 import Control.Monad.Error.Trans
@@ -120,6 +121,9 @@ lookAhead (ParserT p) = ParserT \s -> do
   state <- p s
   return state{input = s, consumed = false}
 
+notFollowedBy :: forall s a m. (Monad m) => ParserT s m a -> ParserT s m Unit
+notFollowedBy p = try $ (try p *> fail "Negated parser succeeded") <|> return unit
+
 manyTill :: forall s a m e. (Monad m) => ParserT s m a -> ParserT s m e -> ParserT s m [a]
 manyTill p end = scan
   where