Darren Duncan wrote:
Also, I don't agree with the notion of a header of each relation. It
has a type for each tuple item, sure, but header just sounds like the
sort of thing you want in a ResultSet, not a Relation.
Sam.
A relation's heading is essentially the definition of the relation's
Prompted by Darren Duncan's proposal on Relation type objects
I looked at http://dev.perl.org/perl6/doc/design/syn/S06.html
and wondered how Interval type objects would fit in.
I couldn't imagine how. Now that isn't a surprise
(not for lack of imagination but for lack of perl6 knowledge).
I
At 3:06 PM +0200 5/6/06, mAsterdam wrote:
Prompted by Darren Duncan's proposal on Relation type objects
I looked at http://dev.perl.org/perl6/doc/design/syn/S06.html
and wondered how Interval type objects would fit in.
I couldn't imagine how. Now that isn't a surprise
(not for lack of
On Sat, May 06, 2006 at 01:41:41PM -0700, Darren Duncan wrote:
: Some people may confuse it with a Range, but I don't think so since a
: Range progresses in discrete increments, while an Interval would be
: continuous.
No, Range objects in Perl 6 are defined to be intervals unless used
in a
On Sat, May 06, 2006 at 01:41:41PM -0700, Darren Duncan wrote:
Some people may confuse it with a Range, but I don't think so since a
Range progresses in discrete increments, while an Interval would be
continuous.
A range listifies to a (potentially) finite list of discrete elements, but
it
At 2:03 PM -0700 5/6/06, Larry Wall wrote (in reply):
No, Range objects in Perl 6 are defined to be intervals unless used
in a context that implies discrete increments, such as counting in
list context. But if you say
$x ~~ 1.2 ..^ 3.4
it is exactly equivalent to
1.2 = $x 3.4
The
Darren Duncan wrote:
mAsterdam wrote:
Prompted by Darren Duncan's proposal on Relation type objects
I looked at http://dev.perl.org/perl6/doc/design/syn/S06.html
and wondered how Interval type objects would fit in.
I couldn't imagine how. Now that isn't a surprise
(not for lack of imagination
Darren Duncan wrote:
At 2:03 PM -0700 5/6/06, Larry Wall wrote (in reply):
No, Range objects in Perl 6 are defined to be intervals unless used
in a context that implies discrete increments, such as counting in
list context. But if you say
$x ~~ 1.2 ..^ 3.4
it is exactly equivalent to
At 12:45 AM +0200 5/7/06, mAsterdam wrote:
Okay, thank you both for clarifying this.
Conceptually in my mind, a Range is entirely appropriate to
represent a mathematical interval, but I was mistaken about Range
being more constrained than it actually is.
So, there you go mAsterdam; Range is
Darren Duncan wrote:
At 12:45 AM +0200 5/7/06, mAsterdam wrote:
Okay, thank you both for clarifying this.
Conceptually in my mind, a Range is entirely appropriate to represent
a mathematical interval, but I was mistaken about Range being more
constrained than it actually is.
So, there you
At 2:17 AM +0200 5/7/06, mAsterdam wrote:
I hope (and think) you are right about that regarding
implementing relations. Using them correctly is another
story though. I don't think Date, Darwen Lorentzos
lightly took the step of introducing 6NF in 2003.
Aside, about RVA (relation valued
At 6:06 PM -0700 5/6/06, Darren Duncan wrote:
You can do it simply, kind of like this:
class Point { has Real $x; has Real $y; };
subset Interval of Range where { all( .items ).does(Real) };
Er, you should read 'Real' as 'Num' (I originally meant Rational,
which no longer exists in the
On Sat, May 06, 2006 at 06:15:34PM -0700, Darren Duncan wrote:
: Er, you should read 'Real' as 'Num' (I originally meant Rational,
: which no longer exists in the newest S06);
Rational still exists in S02--we just don't automatically promote
anything to it currently. (A pragma could change that
Darren Duncan wrote:
At 2:17 AM +0200 5/7/06, mAsterdam wrote:
I hope (and think) you are right about that regarding
implementing relations. Using them correctly is another
story though. I don't think Date, Darwen Lorentzos
lightly took the step of introducing 6NF in 2003.
Aside, about RVA
Darren Duncan wrote:
Is there a reference for the meaning of these methods?
There are many written references to these methods; just type
relational algebra into Google.
I will add that the first hit on such a search, the Wikipedia page on
relational algebra (
At 8:01 PM +1200 5/5/06, Sam Vilain wrote:
Also, I don't agree with the notion of a header of each relation. It
has a type for each tuple item, sure, but header just sounds like the
sort of thing you want in a ResultSet, not a Relation.
Sam.
A relation's heading is essentially the definition
First of all, Sam Vilain, thank you for your responses.
Giving these issues more thought, I'm am now leaning towards the idea
that the best way to provide relational algebra in Perl 6 is that the
relation-land Tuple and Relation each be a Role which various other
classes can provide to their
As I carry on in my spare time to implement a Relation type for Perl
6, I would like to use some of the simpler types that were added to
the Synopsis recently and seem to lack a lot of explanatory details
that older types have, and moreover they don't seem to be implemented
yet in Pugs.
So I
Darren Duncan wrote:
Speaking a little more technically, a Relation has 2 main components,
its heading and its body. The heading is a set of 0..N keys (called
attributes in relation-land), and the body is a set of 0..N
Mappings (called tuples in relation-land), where they set of keys
of each
At 10:51 AM +1200 5/5/06, Sam Vilain wrote:
Moreover, the Relation type has these
operators that the Set type doesn't have: rename(), project(),
restrict(), extend(), join(), divide(), summarize(), group(),
ungroup(), wrap(), unwrap(), matching(), etc.
Is there a reference for the meaning
Actually, I'll add a few more things to my reply, which should be helpful ...
At 5:11 PM -0700 5/4/06, Darren Duncan wrote:
At 10:51 AM +1200 5/5/06, Sam Vilain wrote:
Moreover, the Relation type has these
operators that the Set type doesn't have: rename(), project(),
restrict(), extend(),
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