List comprehension in a few (non-syntax checked) lines. TL;DR: list
comprehension = monadic combinators.

let return a = [a]
let (>>=) x f = List.(flatten (map f x))
let (>>) x y = x >>= fun () -> y
let guard b = if b then [()] else []

With these combinators

[ f (x,y) | x <- l ; y <-r ; x=y+1 ]

then translates to

l >>= fun x ->
r >>= fun y ->
guard (x=y+1) >>
return (f x)

Less compact, no doubt, but still reasonably practical.


On 7 March 2014 23:12, Simon Cruanes <simon.cruanes.2007@m4x.org> wrote:

> Le Fri, 07 Mar 2014, Yotam Barnoy a écrit :
>
> > I have a question about Batteries Included. Specifically, how do I get
> the
> > syntax extensions working and which syntax extensions are available? The
> > various bits of documentation I've found seemed either contradictory or
> did
> > not mention any syntax extensions at all. I'm specifically interested in
> > things like automatic rope generation and list comprehensions.
>
> Hi!
>
> The current version of Batteries is 2.2.0 and its documentation is here:
> http://ocaml-batteries-team.github.io/batteries-included/hdoc2/ . As far
> as I know, there are no more syntax extensions in Batteries since 2.0.0
> (which explains why it doesn't depend on camlp4). I don't know much
> about the "rope generation" you talk about, but list comprehensions are
> nicely replaced (imho) by the |> operator:
>
> List.range 1 `To 10
>     |> List.filter (< 5)
>     |> List.map string_of_int
>
> You can ask more questions on the Batteries mailing list
> ( https://lists.forge.ocamlcore.org/cgi-bin/listinfo/batteries-devel ).
> Hope you will find it helpful!
>
> Cheers,
>
> --
> Simon
>
> http://weusepgp.info/
> key 49AA62B6
> fingerprint 949F EB87 8F06 59C6 D7D3  7D8D 4AC0 1D08 49AA 62B6
>