Hi Andrew (Bromage),

       I reversed the parameter order to Data.Map.lookup and calling fromJust to pull out value from Maybe wrapper ... all as you suggested:

> remLookupFwd :: (ReVars m t) => SimplRe t -> ReM m t (ReInfo t)
> remLookupFwd re
>   = do fwd <- gets resFwdMap
>        let { Just reinfo = fromJust(M.lookup re fwd) }                    -- PROBLEM
>        return reinfo

I am still getting a type mismatch:

Swish\HaskellRDF\Dfa\Dfa.lhs:162:29:
    Couldn't match expected type `Maybe t'
           against inferred type `ReInfo t1'
    In the expression: fromJust (M.lookup re fwd)
    In a pattern binding: Just reinfo = fromJust (M.lookup re fwd)
    In the expression:
        do fwd <- gets resFwdMap
           let Just reinfo = fromJust (M.lookup re fwd)
           return reinfo

Vasili