[Camlp4][trivial ?] Anonymous bind (for monads)

Gabriel Kerneis
2007-07-31T16:55:19Z

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Hello,

I've got a little problem with camlp4. The following works perfectly
well :
#####################################################################
~/ocaml/camlp4% cat pa_bind.ml
module Id = struct
let name = "pa_bind"
let version = "$Id:$"
end

module Example (Syntax : Camlp4.Sig.Camlp4Syntax) = struct
include Syntax

EXTEND Gram
expr: LEVEL "top"
[[ t=expr; "foo"; f=expr ->
<:expr<
Lwt.bind $t$ (fun () -> $f$)
>>]];
END
end

module M = Camlp4.Register.OCamlSyntaxExtension(Id)(Example)

~/ocaml/camlp4% ocamlc -c -pp camlp4of -I +camlp4 pa_bind.ml

~/ocaml/camlp4% cat test_bind.ml
let r = (Lwt_unix.sleep 5) foo (print_endline "42")

~/ocaml/camlp4% camlp4of -parser pa_bind.cmo test_bind.ml
let r = Lwt.bind (Lwt_unix.sleep 5) (fun () -> print_endline "42")

#####################################################################

But if I change "foo" to ">>" (which is the usual way to write an
anonymous bind for monads), it doesn't work anymore. I first thought the
reason was that ">>" is also the symbol for closing a quotation, but
trying "++" instead proved useless as well.

I'm certainly not a camlp4 guru so... what am I missing?

Thanks a lot.

Regards,
--
Gabriel

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