Re: [Caml-list] destructive local opens

[Hendrik Boom <hendrik@topoi.pooq.com>]

On Mon, Aug 03, 2015 at 05:51:24PM +0100, Daniel Bünzli wrote:
> Le lundi, 3 août 2015 à 17:13, octachron a écrit :
> > > The benefit is that I can understand what is happening by only looking at the expression I'm reading. With your proposal I also need to go read the library source to understand what is happening.
> >  
> > I think that it is partially true. For instance, with a vector library,  
> > "*" is always quite ambiguous: Is this the original scalar  
> > multiplication? The vector product? The tensor product? The external  
> > product? The Clifford algebra product? These ambiguities already needs  
> > to be resolved in the documentation;
> 
> 
> Note that what you raise here is a different issue it's not about 
> knowing *if* the operator is the one from M.() or the one in scope, 
> but which one is implemented. Very often this can be disambiguised by 
> the surrounding context and, if your operator are few (which they 
> should be), is learnable in practice.
> 
> With the operator warning splitting rule. The inferences are very 
> simple:
> 
> 1. Given a M.( * ) without warning the * may be the one of M or the 
> one in scope. Ambiguous, can't be resolved locally.
> 
> 2. Given a M.( id ) without warning, if [id] is in scope I *know* 
> this [id] is being used. If it's not I know M.id is being used. No 
> ambiguity, can be resolved locally.
> 
> If you allow each identifier in a module to sport an @shadow 
> annotation you lose 2. which I find a  very valuable property. 
> Without it, given that identifiers are much more widespread than 
> operators, we get a much more ambiguous language.

It is important that simple deductions enable the reader to understand 
what a program means.

With a statically checking compiler (what other kind is really useful) 
I rely on the absence of error messages when I perform these simple 
deductions.

Therefore I prefer to either have an explicit error message or an 
explicit disambiguation.

-- hendrik