On Wed, 14 Apr 2010 19:37:22 +1000, Roman Leshchinskiy wrote: > On 14/04/2010, at 09:05, Xiao-Yong Jin wrote: >> I want to use 'mapM' on Data.Vector.Vector, but it looks >> like the only 'mapM' defined is in >> Data.Vector.Fusion.Stream.Monadic. I'm able to use 'stream' >> and 'liftStream' to convert a 'Vector' to a monadic stream, >> on which I can use 'mapM'. But I couldn't find a way to >> convert the monadic stream back to Vector without using an >> intermediate list. I don't think I understand the internal >> of monadic stream that much. But it looks not so fusion to >> me. Is it the only way back to Vector?
> Unfortunately, it's not at all clear to me how to > implement mapM on vectors/arrays without going through an > intermediate list for arbitrary monads (it's easy for ST > and IO). The next version of vector will include mapM and > friends but it will probably be implemented much like you > describe, with appropriate specialisations for ST and IO. > Roman Thanks for the reply. I am using it for 'Either a', but I guess the performance wouldn't be worse than 'mapM' on an Array. I am OK with it. - jxy -- J c/* __o/* X <\ * (__ Y */\ < _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
