create separate module for generic parser combinator utility functions

create separate module for the error formatting wrapper
heavily refactor the typename parser to remove almost all trys,
  convert to applicative only, and left factor nicely
other refactoring to use more idiomatic parsing and to convert to
  applicative only

Language/SQL/SimpleSQL/Errors.lhs

@@ -0,0 +1,51 @@
+
+> -- | helpers to work with parsec errors more nicely
+> module Language.SQL.SimpleSQL.Errors
+>     (ParseError(..)
+>     --,formatError
+>     ,convParseError
+>     ) where
+
+> import Text.Parsec (sourceColumn,sourceLine,sourceName,errorPos)
+> import qualified Text.Parsec as P (ParseError)
+
+> -- | Type to represent parse errors.
+> data ParseError = ParseError
+>                   {peErrorString :: String
+>                    -- ^ contains the error message
+>                   ,peFilename :: FilePath
+>                    -- ^ filename location for the error
+>                   ,pePosition :: (Int,Int)
+>                    -- ^ line number and column number location for the error
+>                   ,peFormattedError :: String
+>                    -- ^ formatted error with the position, error
+>                    -- message and source context
+>                   } deriving (Eq,Show)
+
+> convParseError :: String -> P.ParseError -> ParseError
+> convParseError src e =
+>     ParseError
+>     {peErrorString = show e
+>     ,peFilename = sourceName p
+>     ,pePosition = (sourceLine p, sourceColumn p)
+>     ,peFormattedError = formatError src e}
+>   where
+>     p = errorPos e
+
+format the error more nicely: emacs format for positioning, plus
+context
+
+> formatError :: String -> P.ParseError -> String
+> formatError src e =
+>     sourceName p ++ ":" ++ show (sourceLine p)
+>     ++ ":" ++ show (sourceColumn p) ++ ":"
+>     ++ context
+>     ++ show e
+>   where
+>     context =
+>         let lns = take 1 $ drop (sourceLine p - 1) $ lines src
+>         in case lns of
+>              [x] -> "\n" ++ x ++ "\n"
+>                     ++ replicate (sourceColumn p - 1) ' ' ++ "^\n"
+>              _ -> ""
+>     p = errorPos e