On Fri, Nov 23, 2012 at 11:54:40AM +0000, Wojciech Meyer 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.
> 

Yeah, I saw that.  I will install it and have a look.

> > 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.
> 

Ok, I had only seen the Monad module in batteries.  Also, I tend not
to like batteries as it bloats the executable size; I get something
like a 5MB executable for a small amount of code.

In general, what I would like in a "monad library" would be a
collection of "standard monads".  I am using scarequotes because I
don't know what all of this means.  Looking at the Haskell Wiki
(http://www.haskell.org/haskellwiki/Monad#Common_monads) lists the
common monads as "Maybe, List, State, Reader, and IO".  I would assume
that a monad library would have these and a method for building new
ones.

> 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].

Great.  Thanks for the info!

Chris

> 
> -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/