> > From: Francesco Mazzoli <f...@mazzo.li> > > At Sat, 10 Nov 2012 15:16:30 +0100, > Alberto G. Corona wrote: > > There is a ListLike package, which does this nice abstraction. but I > don't > > know if it is ready for and/or enough complete for serious usage. I?m > > thinking into using it for the same reasons. > > > > Anyone has some experiences to share about it? > > I've used it in the past and it's solid, it's been around for a while and > the > original author knows his Haskell. > > Things I don't like: > > * The classes are huge: > < > http://hackage.haskell.org/packages/archive/ListLike/3.1.6/doc/html/Data-ListLike.html#t:ListLike > >. > I'd much rater prefer to have all those utilities functions outside the > type > class, for no particular reason other then the ugliness of the type > class. >
Speaking as the ListLike maintainer, I'd like this too. But it's difficult to do so without sacrificing performance. In some cases, sacrificing *a lot* of performance. So they have to be class members. However, there's no reason ListLike has to remain a single monolithic class. I'd prefer an API that's split up into several classes, as was done in Edison. Then 'ListLike' itself would just be a type synonym, or possibly a small type class with the appropriate superclasses. However this seems like a lot of work for relatively little payoff, which makes it a low priority for me. * It defines its own wrappers for `ByteString': > < > http://hackage.haskell.org/packages/archive/ListLike/3.1.6/doc/html/Data-ListLike.html#t:CharString > >. > The community's view on newtypes is funny. On the one hand, I see all the time the claim "Just use a newtype wrapper to write instances for ..." (e.g. the recent suggestion of 'instance Num a => Num (a,a)'. On the other, nobody actually seems to want to use these newtype wrappers. Maybe it clutters the code? I don't know. I couldn't think of a better way to implement this functionality, patches would be gratefully accepted. Anyway, you really shouldn't use these wrappers unless you're using a ByteString to represent ASCII text. Which you shouldn't be doing anyway. If you're using a ByteString to represent a sequence of bytes, you needn't ever encounter CharString. > * It doesn't have instances for `Text', you have to resort to the > `listlike-instances' package. > Given that text and vector are both in the Haskell Platform, I wouldn't object to these instances being rolled into the main ListLike package. Any comments on this? John L.
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