Haskellians, The code pasted in below causes Happy to return parE when invoked with happy rparse.y -i . Is there anyway to get Happy to give me just a wee bit more info as to what might be causing the parE (which i interpret a 'parse error'). Best wishes, --greg { module Main where } %name rparse %tokentype { Token } %error { parseError } %token '{' { TokenLCurly } '}' { TokenRCurly } '[' { TokenLSquare } ']' { TokenRSquare } '(' { TokenLRound } ')' { TokenRRound } '@' { TokenAt } ',' { TokenComma } ';' { TokenSemi } lquote { TokenLQuote } rquote { TokenRQuote } %% Molecule : '{' '}' { Zero } | Name Reagent { Locate $1 $2 } | '@' Name { Decode $2 } ReagentList : Reagent { [ $1 ] } | ReagentList ';' Reagent { $1 ++ [$3] } Reagent : '?' '(' NameList ')' Mixture { Abstraction $3 $5 } | '[' Mixture ']' { Concretion $2 } Mixture : Molecule { Mix [ $1 ] } | '{' ReagentList '}' { Mix $2 } NameList : Name { [ $1 ] } | NameList ',' Name { $1 ++ [$3] } Name : lquote Mixture rquote { Name $2 } { parseError :: [Token] -> a parseError _ = error "Parse error" data Molecule = Zero | Locate Name Reagent | Decode Name deriving (Eq, Show) data Reagent = Abstraction [Name] Mix | Concretion Mix deriving (Eq, Show) data Mix = Mix [Molecule] deriving (Eq, Show) data Name = Name Mix deriving (Eq, Show) data Token = TokenLQuote | TokenRQuote | TokenLCurly | TokenRCurly | TokenLSquare | TokenRSquare | TokenLRound | TokenRRound | TokenComma | TokenSemi | TokenAt deriving Show lexer :: String -> [Token] lexer [] = [] lexer (c:cs) | isSpace c = lexer cs lexer ('{':cs) = TokenLCurly : lexer cs lexer ('}':cs) = TokenRCurly : lexer cs lexer ('[':cs) = TokenLSquare : lexer cs lexer (']':cs) = TokenRSquare : lexer cs lexer ('(':cs) = TokenLRound : lexer cs lexer (')':cs) = TokenRRound : lexer cs lexer (',':cs) = TokenComma : lexer cs lexer (';':cs) = TokenSemi : lexer cs lexer ('@':cs) = TokenAt : lexer cs lexer ('<':'<':cs) = TokenLQuote : lexer cs lexer ('>':'>':cs) = TokenRQuote : lexer cs main = getContents >>= print . rparse . lexer } -- L.G. Meredith Managing Partner Biosimilarity LLC 505 N 72nd St Seattle, WA 98103 +1 206.650.3740 http://biosimilarity.blogspot.com