when I type
value x ~num(num=3) y = num > 0 ;
--> value x: ~?num:int -> bool

However, the signature can not be parsed by Camlp4 
however, I tried parse_sig "value x : ?num:int -> bool ;", it's ok,

This seems to be a bug in the printer.
(By the way, it is not useful to declare an optional argument as last parameter of a function, because it cannot be erased. You will have to pass it explicitely (otherwise caml couldn't make the difference between writing the function and writing the function application, writing (x ~num:None) to get the default value).

 module X : sig type a = int; and b = (int * int); end
you can see the semi is redudant, it is an error?

Again, this looks like a printer issue. The correct syntax has no semicolon before "and":  (type .. and .. and ...) is a single phrase.

For a relatively comprehensive documentation of the revised syntax¹, see
  http://caml.inria.fr/pub/docs/tutorial-camlp4/tutorial005.html
(This is the revised syntax as of camlp4 < 3.10, and possibly Camlp5; in current versions of Camlp4 I think the rules have been slightly relaxed, but that it is backward-compatible.)

2011/5/9 bob zhang <bobzhang1988@gmail.com>
Hi, all,
I am not sure that I made a mistake or two minor bugs in camlp4 revised
syntax?

Both cases are in toploop, after I type

#camlp4r;;
#load "camlp4rf.cma";
Register.loaded_modules;
- : ref (list string) =
{Pervasives.contents=
["Camlp4ListComprenhsion"; "Camlp4MacroParser"; "Camlp4MacroParser";
"Camlp4GrammarParser"; "Camlp4OCamlRevisedParserParser";
"Camlp4QuotationExpander"; "Camlp4OCamlRevisedParser"]}


case1:
for the signature parsing,

when I type
value x ~num(num=3) y = num > 0 ;
--> value x: ~?num:int -> bool

However, the signature can not be parsed by Camlp4
value parse_sig = Camlp4.PreCast.Syntax.(Gram.parse_string sig_item
Loc.ghost);

parse_sig "value x : ~?num:int -> bool;" will raie an exception
however, I tried parse_sig "value x : ?num:int -> bool ;", it's ok,

- : Camlp4.PreCast.Syntax.Ast.sig_item =
Camlp4.PreCast.Syntax.Ast.SgVal <abstr> "x"
(Camlp4.PreCast.Syntax.Ast.TyArr <abstr>
(Camlp4.PreCast.Syntax.Ast.TyOlb <abstr> "num"
(Camlp4.PreCast.Syntax.Ast.TyId <abstr>
(Camlp4.PreCast.Syntax.Ast.IdLid <abstr> "int")))
(Camlp4.PreCast.Syntax.Ast.TyId <abstr>
(Camlp4.PreCast.Syntax.Ast.IdLid <abstr> "bool")))
case 2:
when I type
module X = struct type a = int and b = (int * int); end;
in the toploop
module X : sig type a = int; and b = (int * int); end
you can see the semi is redudant, it is an error?

I thought Camlp4 was heavily used in bootstrapping itself, did I make
some stupid assumptions??

Thanks




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