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 t
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 (
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
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 newes
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 attibut
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 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 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
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
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
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
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 cont
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 imaginatio
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 tried
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 definitio
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
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(), j
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
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
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