Re: Why stack can hold indefinite objects but records cannot?

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2017-11-28 21:31, Victor Porton wrote:
> Why is it OK to create an indefinite object as a local variable ("on stack")
> but not OK to put an indefinite object into a record?

It is OK in both cases. You must provide the constraint that is.

> By the way, how indefinite local variables can be implemented? (just
> curious)

They cannot, there is no such thing.

A variable can hold a value which constraints vary. Each value is 
constrained. These either deploy a maximum allocation length like 
bounded strings or hidden referential semantics like unbounded strings.

> Moreover, wouldn't it to be a good idea to allow indefinite objects in
> records (thus making the record itself indefinite, even if it has no
> discriminants)?

It is a bad idea because there is no straightforward implementation of.

The proper solution is to have an abstract record interface which would 
allow anything appear a record member whereas the implementation would 
be left to the user. The compiler should provide simple implementation 
of that out of the box, maybe even less than it does already.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de