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From: Brighten Godfrey <pbg@cs.berkeley.edu>
Subject: Re: [Caml-list] Record field label locality
Date: Wed, 13 Aug 2008 02:30:02 -0700
To: Richard Jones <rich@annexia.org>,
	blue storm <bluestorm.dylc@gmail.com>,
	Jon Harrop <jon@ffconsultancy.com>,
	OCaml List <caml-list@yquem.inria.fr>
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X-Spam: no; 0.00; locality:01 annotations:01 ocaml:01 ocaml:01 compiler:01 inference:01 undecidable:01 ocaml's:01 nodes:01 nodes:01 'open:01 graph':01 trade-offs:01 frisch:01 camlp:01 

On Aug 13, 2008, at 1:14 AM, Richard Jones wrote:

> On Tue, Aug 12, 2008 at 02:03:46PM -0700, Brighten Godfrey wrote:
>> I think I see what you're getting at.  Is it possible to define
>> compositionality as follows?:
>
> I think Jon means that you can copy and paste code around and it still
> works.

(...which is not true for various other reasons (e.g. conflicting  
type annotations, variables with different types, etc.).)

>> "Removing a type annotation from
>> correct OCaml code results in correct OCaml code."
>
> This is mostly correct.  However very occasionally it is necessary to
> help the compiler out by annotating expressions with types.  I believe
> this is because type inference used by OCaml is undecidable.  You'll
> notice this effect more often if you use OCaml's object system.

Yes, I've noticed that.


> You might want to try renaming the Graph module, ie:
>
>   module G = Graph
>
>   ... g.G.nodes ...
>
> Or if you have control over the module itself, you could also try
> renaming the fields to make them unique (eg. g_nodes), at which point
> you can just 'open Graph'.  There are different trade-offs to each
> approach.

On Aug 12, 2008, at 6:51 PM, blue storm wrote:
> It might be a bit off-topic, but if you want to ease the syntaxic  
> pain only, you can use the pa_openin (http://alain.frisch.fr/ 
> soft.html#openin ) camlp4 extension :
>
>   open Graph in { g with nodes = foo }


Thanks to both of you for suggesting these workarounds.  Probably  
renaming the module is the easiest and least likely to cause other  
problems.  I am still curious about the language design question  
though...

Thanks,
~Brighten