Re: [Caml-list] Re: Why isn't -rectypes command line option the default

[Gerd Stolpmann <info@gerd-stolpmann.de>]

Am Mittwoch, den 21.03.2007, 13:13 +1100 schrieb Erik de Castro Lopo:
> Zheng Li wrote:
> 
> > So the main consideration is safety, though it's really fun to play with
> > recursive types sometimes.
> 
> Ok, I can see why they aren't on by default, but using -rectypes on 
> the whole file exposes to the whole file to these errors.
> 
> Wouldn't it be nicer to be able to specify the rectypes behaviour
> per type? Maybe something like this would work:
> 
> 	rec type 'a t = 'a * 'a t Lazy.t

You can do that:

type 'a t = T of 'a * 'a t Lazy.t

Recursive types are accepted without -rectypes when the recursion
crosses a variant type. Note that the runtime costs are usually
negligible.

Gerd
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