d1 and d2 are numbers we can store as doubles (8 bytes).
d1 > 0
d2 > 0
d1 < d2
Now s1 and s2 are strings of length 8 bytes. (We can ignore unicode here).
Into s1 and s2 we copy the 8 bytes from d1 and d2 respectively.
Does it follow that s1<s2, (or s1 is ordered before s2) when sorted on a
text or binary compare?
Why?
Why do I ask? Well, if we could prove that this is so (s1<s2 => d1<d2) then
we could order arrays of numbers by using the Wizhook.SortStr ingArray
method.
Why would I want to do that? ... No particular reason ... I have a bunch of
other sorting procedures.
--
Lyle
(for e-mail refer to http://ffdba.com/contacts.htm) 14  2006 
WizHook is in A03 so it's safe to use for a while even though it's hidden
and undocumented.
Interesting talk about it here though: http://www.utteraccess.com/forums/ac...ess561560.html
--
Jerry Boone
Analytical Technologies, Inc. http://www.antech.biz
Secure Hosting and Development Solutions for ASP, ASP.NET, SQL Server, and
Access
"Lyle Fairfield" <Mi************ @Invalid.Com> wrote in message
news:Xn******** **********@130. 133.1.4... d1 and d2 are numbers we can store as doubles (8 bytes).
d1 > 0
d2 > 0
d1 < d2
Now s1 and s2 are strings of length 8 bytes. (We can ignore unicode here).
Into s1 and s2 we copy the 8 bytes from d1 and d2 respectively.
Does it follow that s1<s2, (or s1 is ordered before s2) when sorted on a
text or binary compare?
Why?
Why do I ask? Well, if we could prove that this is so (s1<s2 => d1<d2)
then we could order arrays of numbers by using the Wizhook.SortStr ingArray
method.
Why would I want to do that? ... No particular reason ... I have a bunch
of other sorting procedures.
--
Lyle
(for e-mail refer to http://ffdba.com/contacts.htm)
Lyle Fairfield wrote: d1 and d2 are numbers we can store as doubles (8 bytes).
d1 > 0
d2 > 0
d1 < d2
Now s1 and s2 are strings of length 8 bytes. (We can ignore unicode here).
Into s1 and s2 we copy the 8 bytes from d1 and d2 respectively.
Does it follow that s1<s2, (or s1 is ordered before s2) when sorted on a
text or binary compare?
Why?
Why do I ask? Well, if we could prove that this is so (s1<s2 => d1<d2) then
we could order arrays of numbers by using the Wizhook.SortStr ingArray
method.
Why would I want to do that? ... No particular reason ... I have a bunch of
other sorting procedures.
--
Lyle
(for e-mail refer to http://ffdba.com/contacts.htm)
Since they are different storage mediums (ex...how many times do you get the
first 3 bytes of a double?) I would suggest you store them into a string left
padded. Since that method adds overhead, I doubt I'd use it.
We've seen where 1,10,100 come before 2, 20, 200 in a string sort....unless
padded.
Salad <oi*@vinegar.co m> wrote in news:40******** *******@vinegar .com: Lyle Fairfield wrote:
d1 and d2 are numbers we can store as doubles (8 bytes).
d1 > 0
d2 > 0
d1 < d2
Now s1 and s2 are strings of length 8 bytes. (We can ignore unicode
here).
Into s1 and s2 we copy the 8 bytes from d1 and d2 respectively.
Does it follow that s1<s2, (or s1 is ordered before s2) when sorted on
a text or binary compare?
Why?
Why do I ask? Well, if we could prove that this is so (s1<s2 => d1<d2)
then we could order arrays of numbers by using the
Wizhook.SortStr ingArray method.
Why would I want to do that? ... No particular reason ... I have a
bunch of other sorting procedures.
--
Lyle
(for e-mail refer to http://ffdba.com/contacts.htm)
Since they are different storage mediums (ex...how many times do you get
the first 3 bytes of a double?) I would suggest you store them into a
string left padded. Since that method adds overhead, I doubt I'd use
it.
We've seen where 1,10,100 come before 2, 20, 200 in a string
sort....unless padded.
sigh ...
--
Lyle
(for e-mail refer to http://ffdba.com/contacts.htm)
On Jan 19 2004, 01:58 pm, Lyle Fairfield <Mi************ @Invalid.Com>
wrote in news:Xn******** **********@130. 133.1.4: Why do I ask? Well, if we could prove that this is so (s1<s2 => d1<d2)
then we could order arrays of numbers by using the
Wizhook.SortStr ingArray method.
This wouldn't be particularly fast, having first allocate strings then sort
them. So I'd stick with those other procedures. Note that this doesn't
answer your original question.
Why would I want to do that? ... No particular reason ... I have a
bunch of other sorting procedures.
--
(remove a 9 to reply by email)
Thoughts only ...
Depends on how you do the copying, Windows systems are little endian so the
bytes are stuffed in from the left hand side, if you just CopyMemory this it
will be the wrong way around.
Doubles are IEEE 8 byte floating numbers so you would also have a problem
with the sign bit.
Terry
"Lyle Fairfield" <Mi************ @Invalid.Com> wrote in message
news:Xn******** **********@130. 133.1.4... d1 and d2 are numbers we can store as doubles (8 bytes).
d1 > 0
d2 > 0
d1 < d2
Now s1 and s2 are strings of length 8 bytes. (We can ignore unicode here).
Into s1 and s2 we copy the 8 bytes from d1 and d2 respectively.
Does it follow that s1<s2, (or s1 is ordered before s2) when sorted on a
text or binary compare?
Why?
Why do I ask? Well, if we could prove that this is so (s1<s2 => d1<d2)
then we could order arrays of numbers by using the Wizhook.SortStr ingArray
method.
Why would I want to do that? ... No particular reason ... I have a bunch
of other sorting procedures.
--
Lyle
(for e-mail refer to http://ffdba.com/contacts.htm)
On Tue, 20 Jan 2004 16:48:09 -0000, "Terry Kreft"
<te*********@mp s.co.uk> wrote in comp.databases. ms-access: Doubles are IEEE 8 byte floating numbers so you would also have a problem
with the sign bit.
Not really. Lyle made clear he was dealing solely with positive
numbers. The sign bit is zero for positive numbers and 1 for negative
numbers, so its a non-issue for the given problem.
Peter Miller
_______________ _______________ _______________ _______________
PK Solutions -- Data Recovery for Microsoft Access/Jet/SQL
Free quotes, Guaranteed lowest prices and best results www.pksolutions.com 1.866.FILE.FIX 1.760.476.9051
Lyle,
On 19 Jan 2004 18:58:44 GMT, Lyle Fairfield
<Mi************ @Invalid.Com> wrote in comp.databases. ms-access: d1 and d2 are numbers we can store as doubles (8 bytes).
d1 > 0
d2 > 0
d1 < d2
Now s1 and s2 are strings of length 8 bytes. (We can ignore unicode here).
Into s1 and s2 we copy the 8 bytes from d1 and d2 respectively.
Does it follow that s1<s2, (or s1 is ordered before s2) when sorted on a
text or binary compare?
Why?
Who cares why!
Knowledge for knowledge's sake, right? Isn't that good enough a
reason?
As long as you make sure you get the byte order correct, you can do as
you suggest and compare double values as strings. But since, in
vb/vba, you can't simply cast one value as another as you could in c,
c++, pascal etc, how are you doing the psudeo-casting? If you're,
say, reading in the values from a file, its trivial (just read an
eight byte string at the i/o point where the double is stored) but if
you're working solely in memory (ie you have a double variable, and
you store it in a string) then the manner used is, of course,
critical. If you can clarify how you're doing the casting, I can give
a clearer answer on whether there'd be any problems.
But two quick points are already clear. (1), a binary comparison is
preferable and (2) working with double values as strings will be
slower than leaving them as doubles.
Peter Miller
_______________ _______________ _______________ _______________
PK Solutions -- Data Recovery for Microsoft Access/Jet/SQL
Free quotes, Guaranteed lowest prices and best results www.pksolutions.com 1.866.FILE.FIX 1.760.476.9051
Peter Miller <pm*****@pksolu tions.com> wrote in
news:gq******** *************** *********@4ax.c om: As long as you make sure you get the byte order correct, you can do as
you suggest and compare double values as strings. But since, in
vb/vba, you can't simply cast one value as another as you could in c,
c++, pascal etc, how are you doing the psudeo-casting?
API CopyMemory
--
Lyle
(for e-mail refer to http://ffdba.com/contacts.htm)
On 21 Jan 2004 03:36:31 GMT, Lyle Fairfield
<Mi************ @Invalid.Com> wrote:
That seems risky, because of the byte layout, which is not as innocent
people (not sure that includes you :-)) might expect.
As a test, use the longint &HAABBCCDD&, CopyMemory it, and observe
you're not getting the characters for &HAA, &HBB etc in that order.
-Tom. Peter Miller <pm*****@pksolu tions.com> wrote in
news:gq******* *************** **********@4ax. com:
As long as you make sure you get the byte order correct, you can do as
you suggest and compare double values as strings. But since, in
vb/vba, you can't simply cast one value as another as you could in c,
c++, pascal etc, how are you doing the psudeo-casting?
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