Michael Lazzaro [EMAIL PROTECTED] writes:
Solution 1: If you attempt to SET a cell to it's 'empty value', it
will be set to it's default:
my int @a is default(5); #
@a[5] = 0;# actually sets it to it's 'empty
value', 5
@a[5] = undef;# autocnv to 0, + warning, still sets to 5
my Int @a is default(5); # NOTE difference in type!
@a[5] = 0;# THIS really does set it to 0
@a[5] = undef;# and this sets it to 5
So you can't set something to its type's own empty value, because it
will, by definition, thereafter return it's overloaded empty value,
def.
AAARGH, *runs for shelter*
Setting an element to a leagal value, results in a different value to
be stored, making it impossible to store this value. And this is even
the most prominent value of the underlying type.
Solution 2: _ANY_ other solution would require the introduction of
'fake empty' and 'really empty', and require arrays to keep track of
the difference.
my Int @a is default(5);
@a[3] = 3; # there are now 4 items in the array
@a[2]; # was autoset to undef, so returns 5
@a[4]; # doesn't exist, so returns 5
@a[2] = undef; # well, it's still undef, but now mark it
# as a 'real' undef, so don't return 5.
This is essentially adding another layer of defined-ness on each cell,
and therefore requires an additional flag be kept checked for each
array element. While this is certainly a possibility, I worry about
the complexity it introduces.
Solution 3: The autoset sets the value to the default value.
my Int @a is default(5);
@a[3] = 3; # there are now 4 items in the array
@a[2]; # was autoset 5 so returns 5
@a[4]; # doesn't exist, so returns 5
@a[2] = undef; # set to undef, so returns undef
@a[5] = @a.default # if you really want to reset something to
# default. BTW there are now 6 items in
# the array. returns 5
@a[4]; # is now autoset to 5 so it remains 5
The default default value is the empty value of the base type.
my Int @a;
is the same as
my Int @a is default(undef);
bye
b.
--
Juergen Boemmels[EMAIL PROTECTED]
Fachbereich Physik Tel: ++49-(0)631-205-2817
Universitaet Kaiserslautern Fax: ++49-(0)631-205-3906
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