Re: [Caml-list] destructive local opens

[Goswin von Brederlow <goswin-v-b@web.de>]

On Mon, Aug 03, 2015 at 03:24:18PM +0100, Daniel Bünzli wrote:
> Le lundi, 3 août 2015 à 15:08, Nils Becker a écrit :
> > It's possible that people actually want M.() to mean let open! more
> > often than let open. For me I think that's the case.
> 
> If you are in the vector case, I don't think that's the case. With Gg [1] I often had the following kind of subtly wrong code (can't remember the exact details but something similar):  
> 
> let ox = V2.((dot v ox) * ox) in
> V2.(3 * ox + oy)

What is wrong with that code?

I'm assuming V2 has:

val (+): t -> t -> t
val (*): int -> t -> t
val dot: t -> t -> int
 
> The reality is that M.() is inherently dangerous, especially from an API evolution perspective where new identifiers with matching type may get introduced later leading to silent semantic changes in your code. So we should not encourage people to use M.!() as it's going to make the problem even more acute. Besides we should have that 44 warning by default so that we see the problems, but for now it's impossible to live with 44 and a Gg like library.
> 
> Best,
> 
> Daniel
> 
> [1] http://erratique.ch/software/gg

MfG
	Goswin