Chaim Frenkel wrote:
>
> >>>>> "PRL" == Perl6 RFC Librarian <[EMAIL PROTECTED]> writes:
>
> PRL> %DataHash = unpack $mypic, $SomePackedCobolData;
>
> Does it unpack it into the hash? Or does it keep a pointer into
> the original structure?
I'd think it would depend on if %DataHash is defined already. For
unpack() to return a list of key/value pairs is not all that different
from just returning values the way it does now. For unpack to return
a tied object that refers to a copy of the initial data, that is a little
bit more different but it is within possibility.
> What happens when a new key is added to the hash?
that may or may not be possible, I'd like to discuss it further
before declaring one way or the other.
> What happens if the underlying structure is overlayed?
>
> sysread(FOO, $SomePackedCobolData, $length);
> %DataHash = unpack $mypic, $SomePackedCobolData;
> sysread(FOO, $SomePackedCobolData, $length);
>
> <chaim>
Perl data accessors generally create copies to avoid these "action at
a distance" situations such as the case where %DataHash is composed
of offsets into a scalar which gets redefined. Perl5's unpack function
creates copies.
These issues presuppose a "closed hash" data type, and its internal
representation. Why don't you write the RFC that answers these questions?
How would you like to see your coboldata represented and used as a
perl hash?
--
David Nicol 816.235.1187 [EMAIL PROTECTED]
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