Re: [Caml-list] Monad Library?

[David House <dhouse@janestreet.com>]

Of, and of course it features instances for Option.t, Result.t,
Or_error.t, List.t and all the other standard types inside core!

On Fri, Nov 23, 2012 at 12:09 PM, David House <dhouse@janestreet.com> wrote:
> The Core library [1] has a good monad library that gets used in
> basically every single Jane Street program (and notably inside async).
> Among its features are:
>
> * Module types for monads with one or two type parameters
>
> * Functors to make modules satisfying those signatures given just bind + return
>
> * "Infix" submodules which one can locally open ("let open
> Option.Monad_infix in") in order to temporarily work inside another
> monad -- very useful.
>
> It notably does *not* feature a syntax extension to make monadic
> computations look pretty. You must write out the binds and returns
> yourself. To be honest, the reason for this is mostly history, but we
> actually have some anecdotal evidence now that writing in the explicit
> style makes things easier to understand for authors and readers of
> code.
>
> [1]: https://bitbucket.org/yminsky/ocaml-core/wiki/Home
>
>
> On Fri, Nov 23, 2012 at 11:54 AM, Wojciech Meyer
> <wojciech.meyer@googlemail.com> wrote:
>> On Fri, Nov 23, 2012 at 11:43 AM, Chris Yocum <cyocum@gmail.com> wrote:
>>> I was looking into using Monads in my programs but I am slightly at a
>>> loss as to what library is in general use.  There is pa_monad but that
>>
>> pa_monad is really useful and nice, I think the updated library is
>> available as pa_monad_custom OPAM package.
>>
>>> seems to be a ocamlp4 exention and not a library.  There is
>>> http://lambda.jimpryor.net/monad_library/ but that doesn't seem to be
>>> in opam or in godi so I am unsure as to its status.
>>>
>>> Does anyone have any suggestion for a well supported monad library for
>>> Ocaml?
>>
>> First I would need to find an answer what do you mean by a monad library.
>>
>> Monads is a general abstraction with a very simple interface. so they
>> don't require library as such.
>>
>> However I agree it would be good to have some library that provides a
>> monadic interface to some common functionality found maybe in std
>> libraries, also some way of composing monads would be good having
>> monad transformers along. Batteries included offer monadic interface
>> to some common data types like list, bool, option.
>>
>> You could look at Xavier Leroy's lectures here [1] to see the
>> excellent examples of using monads in OCaml.
>>
>> For somewhat advanced type system trickery to use generic interface
>> for monads you can look at this excellent post [2].
>>
>> -Wojciech
>>
>> [1] http://gallium.inria.fr/~xleroy/mpri/progfunc/monads.2up.pdf
>> [2] http://alaska-kamtchatka.blogspot.co.uk/2011/09/higher-order-fun.html
>> [3] http://batteries.forge.ocamlcore.org/
>>
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