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Postings from August 2005
On Sat, Aug 06, 2005 at 12:43:13PM -0400, Matt Fowles wrote:
> The pictures are pretty and the compilation one makes a great deal of
> sense, but I must admit to being enitrely confused by the container
> one. I think part of the problem is that I don't have a good footing
> from which to understand it. Is there somewhere I can look for a
> gentle explanation of the whole container/tied/untied thing?
Hm, I'm afraid there are not much material on this beyond the Synopses,
so I'll try to describe that picture a bit.
First off, all the lines you see are "has-a" relationships. To wit:
Pad has-a Scalar Container that you can look up with "$name".
my $name;
The Container either has-a mutable cell, or has-a constant cell.
my $mut = 3;
my $con := 3;
Use ":=" to change the cell inside a container:
my $x = 3;
my $y = 4;
my $z = 5;
$x := $y; # $x and $y now contain the same cell
$x := $z; # not anymore; $x now shares the cell with $z
Each cell has a Id. Use "=:=" to check whether two containers have
cells of the same Id:
$x =:= $y; # false
$x =:= $z; # true
Mutable cells has-a mutable scalar value. Use "=" to change its value:
$mut = 5; # works
Constant cells has-a immutable scalar value. You cannot change it:
$con = 6; # error
Each cell is declared to be "is Tieable" or not tiable when it was
allocated; you cannot change tieableness at runtime.
my $nvar;
my $tvar is Tieable;
Tieable cells may be tied or untied. Use "tie" to tie a tieable cell:
tie($tvar, SomeClass, some_param => 1);
Non-tieable cells may not be tied. However, "untie" always works:
untie($tvar); # works
untie($nvar); # no-op
That's about it. :-) Hopefully my two questions will make more sense
to you now...
Thanks,
/Autrijus/
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