1 patch for repository http://code.haskell.org/parsec3:

Thu Sep  5 11:12:47 CEST 2013  Petr Pudlak <petr@pudlak.name>
  * Add 'emptyIf' which allows a parser to optinally fail without consuming any input.

New patches:

[Add 'emptyIf' which allows a parser to optinally fail without consuming any input.
Petr Pudlak <petr@pudlak.name>**20130905091247
 Ignore-this: 59b93c660fe860acd9a5fff887f7678f
] {
hunk ./Text/Parsec/Prim.hs 38
     , parserPlus
     , (<?>)
     , (<|>)
+    , emptyIf
     , label
     , labels
     , lookAhead
hunk ./Text/Parsec/Prim.hs 455
     p' = ParsecT $ \s cok cerr eok eerr ->
          unParser p s eok cerr eok eerr
 
+-- | @emptyIf p@ parses @p@ and if its return value is @Nothing@, pretends
+-- that an error has occured with no input consumed.
+--
+-- If @p@ fails and consumes some input, so does @emptyIf p@. Combine with
+-- 'try' if this is undesirable.
+
+emptyIf :: (Stream s m t) => ParsecT s u m (Maybe a) -> ParsecT s u m a
+emptyIf p = ParsecT $ \s cok  cerr eok eerr ->
+                        let cok' (Just x) s e = cok x s e
+                            cok' Nothing  _ e = eerr e
+                            eok' (Just x) s e = eok x s e
+                            eok' Nothing  _ e = eerr e
+                        in unParser p s cok' cerr eok' eerr
+          
+
 -- | The parser @token showTok posFromTok testTok@ accepts a token @t@
 -- with result @x@ when the function @testTok t@ returns @'Just' x@. The
 -- source position of the @t@ should be returned by @posFromTok t@ and
}

Context:

[Fix haddock module links.
Bjorn Buckwalter <bjorn@buckwalter.se>**20130821095713
 Ignore-this: 304217ec8b73f59edcd96dd13aca67af
] 
[TAG 3.1.3
Antoine Latter <aslatter@gmail.com>**20120612020909
 Ignore-this: 7100375a3e4853c09f1ea993ae32eed7
] 
Patch bundle hash:
173111b8bbc5a6eb69d41926053184c35ae9b3cc