Re: [Caml-list] Record field label locality

[Richard Jones <rich@annexia.org>]

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.

> "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.

> I would claim that the current syntax (`g.Graph.nodes' in the above  
> example) is effectively a type annotation that permits the type  
> inference that `g' is a `Graph.t'.  The annoying bit is that you are  
> required to use every single time you use a record in `g'.

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.

Rich.

-- 
Richard Jones
Red Hat