Re: making variables or containers read-only

[John Porter]

David L. Nicol wrote:
> "seal" has been suggested.
> ...
> As for read-only being an attribute, if attributes are compiler hints, how
> do we set something to be read-only then?  And we can't unseal a r-o item
> without making a copy of it. 


Pardon me, but why the fsck is so much time and energy being spent
on this issue?  Read-only-ness will be trivial to implement in perl6,
and presumably it will be done via an attribute.
And it will presumably have a sensible name like "readonly".

If there really must be a function to turn it on and off, wtf
would it be anything less sensible than "make_readonly" or similar?
Trying to overload "close" to the job is just ridiculous.


> Currently nothing in perl enforces access besides lexical visibility
> rules.

This will of course be different in perl6.
If you're hung up on the implementation, please take it
to the -internals list.

Thank you.

-- 
John Porter

making variables or containers read-only

[David L. Nicol]

"Mark J. Reed" wrote:

> If I wanted to make a variable read-only, I would expect to do it
> by setting the read-only attribute on that variable, which I would
> further expect to do the same way I would set any other attribute at
> any other time.  Orthogonality has its good points, even in Perl;
> you just shouldn't be afraid to veer off diagonally when it makes sense.
> I don't think close(var) makes sense.
 
"seal" has been suggested.

Currently nothing in perl enforces access besides lexical visibility
rules.  Lexical visibility makes it possible to create read-only types
by tieing to classes where STORE is a no-op.  Defining a read-only 
implementation is trivial.


I'm experiencing Warnock's dilemma WRT my suggestion that the
make-read-only
operation, whatever it looks like, might return a coderef which could be
run
to unseal the variable/container, or might get not stored, indicating that
the item is permanently read-only and can be optimized as such.


As for read-only being an attribute, if attributes are compiler hints, how
do we set something to be read-only then?  And we can't unseal a r-o item
without making a copy of it. 








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   David Nicol 816.235.1187
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