[Caml-list] [Batteries or Camlp4] Functionaly updating several fields in an object

[Caml-list] [Batteries or Camlp4] Functionaly updating several fields in an object

[Ivan Gotovchits]

I do not know whether the following behaviour is a bug or a feature, so
I've decided to consult with a community.

Given a simple definition:

let create ()  = 
object
  val a = []
  val b = []
  method step = {< a = a; b = b; >}
end

when compiling using batteries extensions:

ocamlfind ocamlc -c -package batteries.syntax -package lablgtk2
-package lablgtk2.init -package oUnit -package threads -package uuidm
-syntax camlp4o -thread -package batteries -syntax camlp4o -I +gsl -I
+res -I +xml-light -I +lablgtk2 -I gui -o gui/bug.cmo gui/bug.ml

I'm receiving the following error:
File "gui/bug.ml", line 7, characters 10-11:
Warning S: this expression should have type unit.
File "gui/bug.ml", line 8, characters 6-11:
Error: This expression has type bool but an expression was expected of type
         'a list

It seems that compilet thinks that something like this:
«a = begin a; b = b end».

After disabling syntax extension everything is ok. 

So the questions:
1) Is this a bug? If not, then how to overcome this unwanted behaviour?
2) If this is a bug? What must be blamed: camlp4 or Batteries?


Thanks in advance, for any comments!

P.S. My setup:
OS: Debian Squeeze 6.0.5
Objective Caml: 3.11.2
Batteries: 1.2.2-1




-- 
         (__) 
         (oo) 
   /------\/ 
  / |    ||   
 *  /\---/\ 
    ~~   ~~   
...."Have you mooed today?"...

Re: [Caml-list] [Batteries or Camlp4] Functionaly updating several fields in an object

[Gabriel Scherer]

It appears to be a parsing bug in the 3.11 version of Camlp4. It
happens neither with 3.10.2 or with more recent version.
(I was lucky to find a machine with 3.11.2 installed; it's good to
have rarely-updated servers around)

Steps to reproduce:
  camlp4o -str 'let _ = {< a = a; b = b >}'
Observed result:
  {< a = (a; b = b); >}

Upgrading to a more recent version of OCaml would solve your problem.
Otherwise, not using syntax extensions is also fine.

On Tue, Oct 23, 2012 at 2:24 PM, Ivan Gotovchits <ivg@ieee.org> wrote:
>
> I do not know whether the following behaviour is a bug or a feature, so
> I've decided to consult with a community.
>
> Given a simple definition:
>
> let create ()  =
> object
>   val a = []
>   val b = []
>   method step = {< a = a; b = b; >}
> end
>
> when compiling using batteries extensions:
>
> ocamlfind ocamlc -c -package batteries.syntax -package lablgtk2
> -package lablgtk2.init -package oUnit -package threads -package uuidm
> -syntax camlp4o -thread -package batteries -syntax camlp4o -I +gsl -I
> +res -I +xml-light -I +lablgtk2 -I gui -o gui/bug.cmo gui/bug.ml
>
> I'm receiving the following error:
> File "gui/bug.ml", line 7, characters 10-11:
> Warning S: this expression should have type unit.
> File "gui/bug.ml", line 8, characters 6-11:
> Error: This expression has type bool but an expression was expected of type
>          'a list
>
> It seems that compilet thinks that something like this:
> «a = begin a; b = b end».
>
> After disabling syntax extension everything is ok.
>
> So the questions:
> 1) Is this a bug? If not, then how to overcome this unwanted behaviour?
> 2) If this is a bug? What must be blamed: camlp4 or Batteries?
>
>
> Thanks in advance, for any comments!
>
> P.S. My setup:
> OS: Debian Squeeze 6.0.5
> Objective Caml: 3.11.2
> Batteries: 1.2.2-1
>
>
>
>
> --
>          (__)
>          (oo)
>    /------\/
>   / |    ||
>  *  /\---/\
>     ~~   ~~
> ...."Have you mooed today?"...
>
> --
> Caml-list mailing list.  Subscription management and archives:
> https://sympa.inria.fr/sympa/arc/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs

Re: [Caml-list] [Batteries or Camlp4] Functionaly updating several fields in an object

[Ivan Gotovchits]

Gabriel Scherer <gabriel.scherer@gmail.com> writes:

> It appears to be a parsing bug in the 3.11 version of Camlp4. It
> happens neither with 3.10.2 or with more recent version.
> (I was lucky to find a machine with 3.11.2 installed; it's good to
> have rarely-updated servers around)
>
> Steps to reproduce:
>   camlp4o -str 'let _ = {< a = a; b = b >}'
> Observed result:
>   {< a = (a; b = b); >}
>
> Upgrading to a more recent version of OCaml would solve your problem.
> Otherwise, not using syntax extensions is also fine.
>

Unfortunately, I cannot upgrade to a more recent version. Because I'm
restricted to use a certified software...

Though, many thanks for clarifying the issue!

-- 
         (__) 
         (oo) 
   /------\/ 
  / |    ||   
 *  /\---/\ 
    ~~   ~~   
...."Have you mooed today?"...

Re: [Caml-list] [Batteries or Camlp4] Functionaly updating several fields in an object

[Edgar Friendly]

On 10/23/2012 9:57 AM, Ivan Gotovchits wrote:
> Unfortunately, I cannot upgrade to a more recent version. Because I'm 
> restricted to use a certified software... Though, many thanks for 
> clarifying the issue! 
Luckily, batteries works just fine without camlp4.  Many people, 
including some of the main developers, use it without camlp4. Simply 
remove the `batteries.syntax` dependency and only depend on `batteries`, 
and the rest of batteries will work correctly.

E.