[Haskell-cafe] Extensible states

[Marcos Viera]

In the following paper we introduced an implementation that performs lookup
in O(log n) and insertion in O(1) by moving some of the work to compile
time.

@INPROCEEDINGS { MVP13,
    AUTHOR = { Martinez, Bruno and Viera, Marcos and Pardo, Alberto },
    TITLE = { Just Do It While Compiling!: Fast Extensible Records in
Haskell },
    BOOKTITLE = { Proceedings of the ACM SIGPLAN 2013 Workshop on Partial
Evaluation and Program Manipulation },
    SERIES = { PEPM '13 },
    YEAR = { 2013 },
    ISBN = { 978-1-4503-1842-6 },
    LOCATION = { Rome, Italy },
    PAGES = { 77--86 },
    NUMPAGES = { 10 },
    DOI = { 10.1145/2426890.2426908 },
    ACMID = { 2426908 },
    PUBLISHER = { ACM },
    ADDRESS = { New York, NY, USA },
    KEYWORDS = { balanced trees, extensible records, haskell, hlist, staged
computation, type-level programming },
    PDF = { http://www.fing.edu.uy/~mviera/papers/pepm13.pdf },
}

Best,
 marcos




On Tue, May 5, 2015 at 6:50 AM, Roman Cheplyaka <roma at ro-che.info> wrote:

> On 05/05/15 12:40, Alberto G. Corona  wrote:
> > Hi,
> >
> > Anyone used some of the extensible record packages to create a kind of
> > extensible state monad?
> >
> > I mean something that besides having "get", "gets" and "put"  would have
> > some kind of "add" and "gets":
> >
> > add :: a -> State ()
> > gets  :: State (Maybe a)
> >
> > or
> >
> > add :: LabelName -> a -> State ()
> > gets :: LabelName -> State (Maybe a)
> >
> >
> > So that I can extend the state without using additional monad
> > transformers. Monad transformers are very hard for beginners and
> > scramble error messages
> >
> > I did the first option for MFlow, hplayground and Transient packages
> > (setSData and getSData). But my solution uses a map indexed by type and
> > this requires a lookup for each access.
> >
> > I would like to know if there is an alternative with no lookups. I´m not
> > obsessed with speed but In some applications the speed may be
> important....
> >
> > Anyone?
>
>
> If you care about the error message quality, you'd rather stay away from
> extensible records.
>
> And if you care about speed, most (all?) extensible records give you
> O(n) access, so you'd be actually better off with a simple (Hash)Map.
>
> Roman
>
>
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