Rick Delaney [EMAIL PROTECTED] writes:
I'd also like to point out that ruby has defaults for hashes but
assigning nil (the equivalent of undef) does not set the default; delete
does.
Yeah, but Hashes aren't Arrays. And vice versa.
--
Piers
Aaron Sherman [EMAIL PROTECTED] writes:
On Wed, 2003-01-29 at 14:54, Jonathan Scott Duff wrote:
Can someone give me a realish world example of when you would want an
array that can store both undefined values and default values and those
values are different?
my @send_partner_email is
Aaron Sherman wrote:
On Tue, 2003-01-28 at 16:23, Leopold Toetsch wrote:
Arrays (or hashes) don't grow on reading - never.
But for less pure forms of reading:
foo(@a[0]);
auto-vivification will have to happen in some cases. e.g. if foo
requires a lvalue parameter.
A lvalue param is
On Fri, Jan 31, 2003 at 05:59:46PM +0100, Leopold Toetsch wrote:
A lvalue param is not strictly reading, but here has to happen something
differently - yes:
IMHO some sort of proxy could be passed here, saying: if you write to
me, this will be at @a[0]. Or auto-vivify the entry.
This is
Dave Mitchell wrote:
On Fri, Jan 31, 2003 at 05:59:46PM +0100, Leopold Toetsch wrote:
IMHO some sort of proxy could be passed here, saying: if you write to
me, this will be at @a[0]. Or auto-vivify the entry.
This is what Perl 5 does at the moment:
$ perl5.8.0 -MDevel::Peek -e 'sub
Jonathan Scott Duff wrote:
The solution I advocate is to allow even primitive types to hold
undef.
Why do you then use a primitive type in the first place?
IMHO:
1) primitive types are what they are - no undef, no attributes, just
e.g. plain integers (or shorts or bits ...)
2) if you
On 29 Jan 2003 14:29:52 -0500, Aaron Sherman wrote (in part):
ajs As for the argument that testing for true non-existentness is a
ajs burden, check out the way Perl5 does this. Hint: there's a central
ajs sv_undef, and that's not what array buckets are initialized to
Either you're dead
On Wed, 2003-01-29 at 16:41, Nicholas Clark wrote:
And the demonstration was as expected?
Yes, of course. If you modify a hash, or look at another hash, you
should not expect the same results. Why would you? More importantly, why
would the conversation threat up until now lead to such an
On Wed, 2003-01-29 at 17:12, Dan Sugalski wrote:
At 12:40 PM -0500 1/29/03, Aaron Sherman wrote:
Elements of a has ARE ordered, just not the way you may expect.
Just to nip this one in the bud...
The bud was back that-a-way about 3 days
If people start assuming that there's *any*
On Wed, 2003-01-29 at 17:50, Spider Boardman wrote:
On 29 Jan 2003 14:29:52 -0500, Aaron Sherman wrote (in part):
ajs As for the argument that testing for true non-existentness is a
ajs burden, check out the way Perl5 does this. Hint: there's a central
ajs sv_undef, and that's not what
On Thursday, January 30, 2003, at 12:03 AM, Leopold Toetsch wrote:
Why do you then use a primitive type in the first place?
IMHO:
1) primitive types are what they are - no undef, no attributes, just
e.g. plain integers (or shorts or bits ...)
2) if you want to store additional information
At 9:53 AM -0800 1/30/03, Michael Lazzaro wrote:
This is leading me to the conclusion that primitive-typed arrays
should not be allowed to have defaults, period, and that attempting
to place one should be a compile-time error. If you want a default,
use CInt instead of an Cint, and it will
On Thursday, January 30, 2003, at 09:55 AM, Dan Sugalski wrote:
At 9:53 AM -0800 1/30/03, Michael Lazzaro wrote:
This is leading me to the conclusion that primitive-typed arrays
should not be allowed to have defaults, period, and that attempting
to place one should be a compile-time error.
--- Michael Lazzaro [EMAIL PROTECTED] wrote:
On Thursday, January 30, 2003, at 12:03 AM, Leopold Toetsch wrote:
Why do you then use a primitive type in the first place?
IMHO:
1) primitive types are what they are - no undef, no attributes,
just
e.g. plain integers (or shorts or
Austin Hastings wrote:
There is no reason why primitive-typed arrays can't have a default. It
is the confusion of default with undef that is causing this
problem.
If I have:
my int @a;
print @a[4];
What comes out?
Notice, there's no is default(woo-woo) in there. Just a plain old
primitive
At 10:54 AM -0800 1/30/03, Mark Biggar wrote:
and if we define a prop is no_default then you get what ever
junk happens to be in memory. (this for even more speed)
That's not going to happen. It's too unsafe, and too open to
corruption attacks.
--
Dan
--- Michael Lazzaro [EMAIL PROTECTED] wrote:
Right, we just can't do the 'undef' thing. OK, so let me see if this
is right yet:
my Int @a is default(2);
@a[5] = 5;
@a[4]; # 2 (autofilled)
@a[5]; # 5
@a[6]; # 2 (out-of-bounds)
undef
On Thursday, January 30, 2003, at 12:49 PM, Austin Hastings wrote:
undef @a[5]; # undefining the element sets it to the default
@a[5]; # 2
@a[5] = undef; # same as above
@a[5]; # 2
undef!!
@a is an array of Int (not int) and can store undef, so no error
On Wednesday 29 January 2003 09:52 pm, Rick Delaney wrote:
On Wed, Jan 29, 2003 at 01:54:10PM -0800, Michael Lazzaro wrote:
On Wednesday, January 29, 2003, at 12:38 PM, Smylers wrote:
That would make the rule very simple indeed:
Assigning Cundef to an array element causes that
On Thursday 30 January 2003 06:49 pm, Andrew Rodland wrote:
On Wednesday 29 January 2003 09:52 pm, Rick Delaney wrote:
On Wed, Jan 29, 2003 at 01:54:10PM -0800, Michael Lazzaro wrote:
On Wednesday, January 29, 2003, at 12:38 PM, Smylers wrote:
I'd also like to point out that ruby has
On Tue, 2003-01-28 at 19:24, Paul Johnson wrote:
If that's not the case, I need to get my head around why, since Perl
*does* distinguish between defined and exists.
But I wish it wouldn't for arrays. That only came about to support
pseudo-hashes which are going / have gone away.
Are
On 2003-01-29 at 09:44:27, Aaron Sherman wrote:
Yes, I would expect that. In my opinion there is no difference between
an array and a hash other than the underlying storage and the
type-management of the key.
Perhaps it is your opinion that those should be the only differences,
but the actual
On 2003-01-29 at 10:32:58, Mark J. Reed wrote:
(What their value should be is the subject of the
parallel thread on array defaults).
Whups, that would be THIS thread, actually. The sidebar on
removing the syntactic distinction between arrays and hashes
made me think I was over in the Spare
--- Jonathan Scott Duff [EMAIL PROTECTED] wrote:
Can I flame you for being too preemptive? :-)
In all honesty, I just wanted to be able to use absquatulate in a
real post. ;-)
=Austin
Ok, I'll respond to a couple of points, below, but I think a lot of
folks are confusing some operational concepts here, and it's getting
hard to un-peel them.
A container has many attributes, even if Perl won't let us control them.
Those include:
1. Storage
2. Conversion of the
OK, I think we agree that 'default' refers to what to put in the
'holes' of an array (or hash, but that's a separate discussion.) When
you overlay a real hash on top of your default values, the default
values show through the holes. So now we just have to define what
holes are.
An
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
--- Michael Lazzaro [EMAIL PROTECTED] wrote:
OK, I think we agree that 'default' refers to what to put in the
'holes' of an array (or hash, but that's a separate discussion.)
When
you overlay a real hash on top of your default values, the default
values show through the holes. So now
On Wed, Jan 29, 2003 at 10:23:26AM -0800, Michael Lazzaro wrote:
OK, I think we agree that 'default' refers to what to put in the
'holes' of an array (or hash, but that's a separate discussion.) When
you overlay a real hash on top of your default values, the default
values show through the
On Wednesday, January 29, 2003, at 11:02 AM, Jonathan Scott Duff wrote:
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.
Looks like a maintenance nightmare to me.
Agreed, it's not pretty. The
Ok, stepping back...
there are three questions:
* Can a type be undefined
* What does an array say when asked for an element that doesn't exist
* What happens when you try to undefine something
I really think you need an attribute to clarify these.
For example, you would not say:
my
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;#
--- Michael Lazzaro [EMAIL PROTECTED] wrote:
On Wednesday, January 29, 2003, at 11:02 AM, Jonathan Scott Duff
wrote:
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.
Looks like a
On Wed, Jan 29, 2003 at 08:49:42PM +0100, Juergen Boemmels wrote:
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]; #
On Wed, Jan 29, 2003 at 11:32:53AM -0800, Michael Lazzaro wrote:
On Wednesday, January 29, 2003, at 11:02 AM, Jonathan Scott Duff wrote:
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.
Looks
Jonathan Scott Duff [EMAIL PROTECTED] writes:
On Wed, Jan 29, 2003 at 08:49:42PM +0100, Juergen Boemmels wrote:
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];
In my opinion, default values for arrays should only come into play
for array elements that have NEVER been assigned to or that have
been explicity undef'ed. If an assigment is made to an array element
then the array element should end up the assigned value (modulo
necessary type conversions) and
On Wed, Jan 29, 2003 at 12:00:33PM -0800, Mark Biggar wrote:
In my opinion, default values for arrays should only come into play
for array elements that have NEVER been assigned to or that have
been explicity undef'ed. If an assigment is made to an array element
then the array element should
On Wed, Jan 29, 2003 at 09:07:37PM +0100, Juergen Boemmels wrote:
Jonathan Scott Duff [EMAIL PROTECTED] writes:
Can someone give me a realish world example of when you would want an
array that can store both undefined values and default values and those
values are different?
Ok, here is
--- Jonathan Scott Duff [EMAIL PROTECTED] wrote:
On Wed, Jan 29, 2003 at 08:49:42PM +0100, Juergen Boemmels wrote:
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];
On Wed, 2003-01-29 at 14:54, Jonathan Scott Duff wrote:
Can someone give me a realish world example of when you would want an
array that can store both undefined values and default values and those
values are different?
my @send_partner_email is default(1);
while $websignups.getline {
On Wed, Jan 29, 2003 at 03:29:57PM -0500, Aaron Sherman wrote:
On Wed, 2003-01-29 at 14:54, Jonathan Scott Duff wrote:
Can someone give me a realish world example of when you would want an
array that can store both undefined values and default values and those
values are different?
my
Agreed, it's not pretty. The fundamental problem is that a primitive
like an Cint simply cannot be undefined... there's no flag for that
(which is they're primitive.)
Certainly there's no way of _storing_ Cundef.
So it having a 'default value' at all is perhaps a bit of a misnomer.
Why
On Wed, 2003-01-29 at 14:53, Austin Hastings wrote:
Leaving out the whole is default() bit, what happens when I:
my int @a;
@a[4] = 100;
@a[2];
What does @a[2] return? It must return something, and that something
can't be undef, because ... above So, what is it? Whatever it
is,
At 10:59 AM -0800 1/29/03, Austin Hastings wrote:
Now: Does this require a fake undef and a real undef?
WHO CARES?
Very good answer. Leave the details to me and the p6i folks. (Though
do please, everyone, pay attention when we tell you that what you
want is slow or awkward)
--
On Wed, Jan 29, 2003 at 03:48:18PM -0500, Dan Sugalski wrote:
(Though do please, everyone, pay attention when we tell you that what
you want is slow or awkward)
Just be sure to reiterate in case we miss it the first time :-)
-Scott
--
Jonathan Scott Duff
[EMAIL PROTECTED]
On Wed, Jan 29, 2003 at 12:40:21PM -0500, Aaron Sherman wrote:
Elements of a has ARE ordered, just not the way you may expect.
Quite:
$ perl5.8.0 -le '%a = (small = 1, large =2); %b = %a; print foreach keys %a; print
--; print foreach keys %b'
large
small
--
small
large
$ perl5.8.0 -le '%a =
On Wednesday, January 29, 2003, at 12:38 PM, Smylers wrote:
That would make the rule very simple indeed:
Assigning Cundef to an array element causes that element to take
the
array's default value.
The effects of this are:
* Assigning a particular integer to an array of int or Int
At 12:40 PM -0500 1/29/03, Aaron Sherman wrote:
Elements of a has ARE ordered, just not the way you may expect.
Just to nip this one in the bud...
If people start assuming that there's *any* ordering to hashes, I
promise I *will* make sure that parrot's external hash class starts
returning
--- Dan Sugalski [EMAIL PROTECTED] wrote:
At 10:59 AM -0800 1/29/03, Austin Hastings wrote:
Now: Does this require a fake undef and a real undef?
WHO CARES?
Very good answer. Leave the details to me and the p6i folks. (Though
do please, everyone, pay attention when we tell you that what
On Wed, Jan 29, 2003 at 02:13:34PM -0600, Jonathan Scott Duff wrote:
On Wed, Jan 29, 2003 at 12:00:33PM -0800, Mark Biggar wrote:
In my opinion, default values for arrays should only come into play
for array elements that have NEVER been assigned to or that have
been explicity undef'ed. If
At 2:18 PM -0800 1/29/03, Austin Hastings wrote:
--- Dan Sugalski [EMAIL PROTECTED] wrote:
At 10:59 AM -0800 1/29/03, Austin Hastings wrote:
Now: Does this require a fake undef and a real undef?
WHO CARES?
Very good answer. Leave the details to me and the p6i folks. (Though
do please,
On Wed, Jan 29, 2003 at 02:37:04PM -0600, Jonathan Scott Duff wrote:
On Wed, Jan 29, 2003 at 03:29:57PM -0500, Aaron Sherman wrote:
On Wed, 2003-01-29 at 14:54, Jonathan Scott Duff wrote:
Can someone give me a realish world example of when you would want an
array that can store both
On Wed, Jan 29, 2003 at 01:54:10PM -0800, Michael Lazzaro wrote:
On Wednesday, January 29, 2003, at 12:38 PM, Smylers wrote:
That would make the rule very simple indeed:
Assigning Cundef to an array element causes that element to take
the
array's default value.
The effects
Jonathan Scott Duff [EMAIL PROTECTED] wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
On Wed, Jan 29, 2003 at 11:32:53AM -0800, Michael Lazzaro wrote:
Agreed, it's not pretty. The fundamental problem is that a primitive
like an Cint simply cannot be undefined... there's no
On Tue, Jan 28, 2003 at 11:15:26AM -0800, Michael Lazzaro wrote:
2) Assume the default value is a simple value, e.g. 'foo'.
my @a is Array( default = 'foo' );
@a[5] = 'bar';
@a[4]; # 'foo'
@a[5]; # 'bar'
@a[6]; # 'foo'
@a[-1];# 'bar'
Michael Lazzaro said:
There has been discussion of allowing a default value for array cells
-- that is, one aside from Cundef or whatever the type-specific
default is. Questions, in order of increased evilness:
1 and 2 seem fine to me.
2a) When a cell is explicitly re-undefined, does the
--- Michael Lazzaro [EMAIL PROTECTED] wrote:
1) What's the final decided syntax? Two possibilities:
my @a is Array( default = 'foo' ); # attrib?
my @a is default('foo');# property?
Since we want arrays (lowercase) to support them, too, it should be a
property.
--- Austin Hastings [EMAIL PROTECTED] wrote:
No, undef. OTOH, deleting @a[1] would reset it to default.
Ere someone flames my for using a hash keyword in an array context:
s/deleting/absquatulating (e.g., via pop, shift, or splice)/
=Austin
I think this debate is easier if you think of defaults as overriding and
auto-vivification method on a container.
On Tue, 2003-01-28 at 14:47, Paul Johnson wrote:
Michael Lazzaro said:
2a) When a cell is explicitly re-undefined, does the default value take
effect?
my @a is Array(
Austin Hastings wrote:
--- Austin Hastings [EMAIL PROTECTED] wrote:
No, undef. OTOH, deleting @a[1] would reset it to default.
Ere someone flames my for using a hash keyword in an array context:
s/deleting/absquatulating (e.g., via pop, shift, or splice)/
Unfortunately, I don't think we
On Tue, Jan 28, 2003 at 12:30:41PM -0800, Austin Hastings wrote:
--- Michael Lazzaro [EMAIL PROTECTED] wrote:
my int @a is Array( default = 5 );
@a[0] = undef;
This should cause a blip of some kind. If storing an explicit undef (as
opposed to undef but 0 or C$v = undef;
Austin Hastings wrote:
Another question: If you ask for a value and get it, does the array
grow? Or does that happen only on assignment? (
Arrays (or hashes) don't grow on reading - never.
And another anser from current low level (list.c classes/Array.pmc)
*Return value
*
On Tue, 2003-01-28 at 16:23, Leopold Toetsch wrote:
Austin Hastings wrote:
Another question: If you ask for a value and get it, does the array
grow? Or does that happen only on assignment? (
Arrays (or hashes) don't grow on reading - never.
Never say never. You're correct for pure
On Tuesday, January 28, 2003, at 01:14 PM, Damian Conway wrote:
I'm not compelled by the counter-argument that this makes it
impossible to store an Cundef in an array with a default. Because
the whole point of an array having a default is to prevent those nasty
out-of-range Cundefs from
On Tuesday, January 28, 2003, at 01:01 PM, Nicholas Clark wrote:
On Tue, Jan 28, 2003 at 12:30:41PM -0800, Austin Hastings wrote:
--- Michael Lazzaro [EMAIL PROTECTED] wrote:
my int @a is Array( default = 5 );
@a[0] = undef;
This should cause a blip of some kind. If storing an
--- Damian Conway [EMAIL PROTECTED] wrote:
Austin Hastings wrote:
--- Austin Hastings [EMAIL PROTECTED] wrote:
No, undef. OTOH, deleting @a[1] would reset it to default.
Ere someone flames my for using a hash keyword in an array context:
s/deleting/absquatulating (e.g., via
Austin Hastings wrote:
--- Austin Hastings [EMAIL PROTECTED] wrote:
No, undef. OTOH, deleting @a[1] would reset it to default.
Ere someone flames my for using a hash keyword in an array context:
s/deleting/absquatulating (e.g., via pop, shift, or splice)/
What's wrong with Cdelete in
--- Michael Lazzaro [EMAIL PROTECTED] wrote:
On Tuesday, January 28, 2003, at 01:01 PM, Nicholas Clark wrote:
On Tue, Jan 28, 2003 at 12:30:41PM -0800, Austin Hastings wrote:
--- Michael Lazzaro [EMAIL PROTECTED] wrote:
my int @a is Array( default = 5 );
@a[0] = undef;
On Tue, Jan 28, 2003 at 02:13:22PM -0800, Michael Lazzaro wrote:
Hmm. I don't have a strong preference either way, but I'm not sure why
(given Cmy int @a):
@a[ undef ]
Cundef should be autoconverted to 0 with warning, but in:
@a[0] = undef;
Cundef should _not_ be
Austin Hastings wrote:
--- Damian Conway [EMAIL PROTECTED] wrote:
my @a is default(666);
print @a[2]; # prints 666
@a[4] = 1;
print @a[2]; # now prints undef :-(
[typo in third line corrected]
I don't understand your example. Can you explain it again, using words
of less than one
Nicholas Clark wrote:
I'm not sure. I think I like the idea of
@a[0] = undef;
being a blip, but
undef @a[0];
resetting the value to the default.
That thought crossed my mind as well before I got to your message ...
Conceptually perl5 already has a distinction between assigning
On Tue, Jan 28, 2003 at 04:07:17PM -0500, Aaron Sherman wrote:
I think this debate is easier if you think of defaults as overriding and
auto-vivification method on a container.
Hmm. I don't :-)
I think it is easier if you think of defaults as overriding undef.
On Tue, 2003-01-28 at 14:47,
On Tue, Jan 28, 2003 at 03:06:19PM -0800, Damian Conway wrote:
Austin Hastings wrote:
--- Damian Conway [EMAIL PROTECTED] wrote:
my @a is default(666);
print @a[2];# prints 666
@a[4] = 1;
print @a[2];# now prints undef :-(
[typo in third line corrected]
Michael Lazzaro wrote:
The next (oft-asked) question is whether or not Cis computed denotes
read-only, or if you can store to an Cis computed array.
my @a is computed { $^index**2 };
@a[4] = 'something completely different';
I'd expect that Cis computed and Cis constant would be
Michael Lazzaro wrote:
2a) When a cell is explicitly re-undefined, does the default value take
effect?
my @a is Array( default = 'foo' ) = (1,2,3);
@a[1] = undef;
@a[1]; # undef, or 'foo'?
STRAWMAN ANSWER: 'foo'.
If Cundef is a valid value for a cell, then I should be
Aaron Sherman wrote:
auto-vivification will have to happen in some cases. e.g. if foo
requires a lvalue parameter. You can't know if an actual write will
happen, so you have to auto-vivify in order to pass a reference.
Or did I miss something there?
I think the idea is to use a special object
So ... with the discussion of what if i really wanted to put an undef in
there b/c it's not just that i haven't defined it but rather that it
really isn't defined. I KNOW it's not defined, and i'm now explicitly
saying it's undefined as opposed to before when i was implicitly
suggesting that i
attriel wrote:
So ... with the discussion of what if i really wanted to put an undef in
there b/c it's not just that i haven't defined it but rather that it
really isn't defined. I KNOW it's not defined, and i'm now explicitly
saying it's undefined as opposed to before when i was implicitly
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