[wg-camlp4] A new branch to experiment with extension points

[Markus Mottl]

It would be great to have one uniform syntax for syntax extensions.  I
don't think we absolutely should keep type_conv like extensions if a
new approach can replace them.  I can understand that industrial users
that have thousands of legacy annotations will not be happy having to
change their sources.  But I think updating sources could be safely
automated to a large extent, and any remaining fixes could be applied
with a little elbow grease.

Regards,
Markus

On Fri, Mar 1, 2013 at 8:40 AM, Gabriel Scherer
<gabriel.scherer at gmail.com> wrote:
> I'm not fond of having "with" as a special case. If you don't support
> the type-conv or deriving syntax as is, could we take this as an
> opportunity to go back to an uniform syntax? Type declaration could be
> handled like any structure item.
>
> Don't we want to have attributes on signature items as well?
>
> Finally, I bet the non-terminal ".." will get little love, but I'm
> sure you considered other option (for example just ;;(:foo), but that
> doesn't work in the toplevel and we really want ";;" to help *avoid*
> precedence issues) and trust that this is one of the less ugly ones.
>
> Is that proposal sufficient to do ocamldoc with structured attributes
> rather than comments? It looks like it is. Can an annotation node, by
> itself, stand as a structure item (I'm thinking section comments)?
>
> On Fri, Mar 1, 2013 at 2:05 PM, Alain Frisch <alain.frisch at lexifi.com> wrote:
>> On 03/01/2013 09:08 AM, Mark Shinwell wrote:
>>>
>>> 1. If possible, I'd rather see one new syntactic form, rather than
>>> three.
>>
>>
>> I've made the syntax more uniform, dropped prefix attributes, and added
>> attributes on type declarations.
>>
>> The current syntax is:
>>
>> Attributes:
>>
>>   On expressions:         expr (:foo expr)
>>   On type expressions:    type (:foo expr)
>>   On structure items:     str_item ..(:foo expr)
>>   On type declarations:   type t = ... with (:foo1 expr1) (:foo2 expr2)
>>
>> Extension nodes:
>>
>>   On expressions:         (&foo expr)
>>   On type expressions:    (&foo expr)
>>   On structure items:     ..(&foo expr)
>>
>>
>> A type-conv like example (attributes on type expressions and type
>> declarations):
>>
>>
>> =================================================
>>  type t = {
>>     x : int (:default 42);
>>     y : int (:default 3) (:sexp_drop_default);
>>     z : int (:default 3) (:sexp_drop_if z_test);
>>  } with (:sexp)
>> =================================================
>>
>>
>> A Bisect-like example (attributes on expressions and structure items):
>>
>> =================================================
>> let f x =
>>   match List.map foo [x; a x; b x] with
>>   | [y1; y2; y3] -> tata
>>   | _ -> (assert false) (:bisect visit)
>>
>>
>> let unused = ()
>> ..(:bisect ignore)
>> =================================================
>>
>>
>> A Bolt-like example (extension nodes on expressions):
>>
>> =================================================
>> let funct n =
>>   (&log) "funct(%d)" n LEVEL DEBUG;
>>   for i = 1 to n do
>>     print_endline "..."
>>   done
>> =================================================
>>
>> or:
>>
>> =================================================
>> let funct n =
>>   (&log "funct(%d)" n LEVEL DEBUG);
>>   for i = 1 to n do
>>     print_endline "..."
>>   done
>> =================================================
>>
>>
>> A map/fold generator (extension nodes on structure item):
>>
>> =================================================
>> type variable = string
>>  and term =
>>   | Var of variable
>>   | Lam of variable * term
>>   | App of term * term
>>
>>
>> ..(&generate_map map term)
>> =================================================
>>
>> or, if we also add extension nodes on class expressions:
>>
>> =================================================
>> type variable = string
>>  and term =
>>   | Var of variable
>>   | Lam of variable * term
>>   | App of term * term
>>
>>
>> class map = (&generate_map term)
>> =================================================
>>
>>
>>
>> -- Alain
>>
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-- 
Markus Mottl        http://www.ocaml.info        markus.mottl at gmail.com