invert(str(xx)) vs str(invert(xx))

[russ Boehle]

Hi all,
I have a field invoiceno which is number 7.0
In A4 the expression "invert(str(invoiceno,7,0))" converted the numeric field to string and inverted the order of the field.
In A5 the same string returns ascii characters.(not useful)
If I change it to str(invert(InvoiceNo),7,0) it changes the numeric value to a negative value and then converts it to string, but gives a valid answer.
Is this odd or am I odd (don't answer that)
Anyway this doesn't seem to work correctly. There is actually more to the expression but it doesn't effect the results here.
Does anyone know what I am doing wrong here?

Thanks
Russ

[Tom Cone Jr]

RE: invert(str(xx)) vs str(invert(xx))

Russ, context is critical. Both expressions should work fine if used to specify an order for your form or report. Neither will work fine if used to specify a calculated value for a field. Actually both work, but the resulting display is meaningless hieroglyphics (sp?). Are you trying to define a calculated field, or are you trying to establish a specific display order for a form or report?

[Tom Cone Jr]

RE: invert(str(xx)) vs str(invert(xx))

... and while I'm at it permit me to pick a small bone.

Why use a numeric type for the invoice number field? Many would recommend that you use a character type for such things...


-- tom

[russ Boehle]

RE: invert(str(xx)) vs str(invert(xx))

Hi Tom,
the expression is an order expression for a lookup. You are right, even though it returns heiroglyphics (sp)is appears to work, alpha creats the same thing when it is done by the program itself.
As far as the invoice number being numeric, this is pretty much historical, I could change it but never saw the need, we've been doing it this way since A4v2 (and before that in CYMA and before that in whatever was before that). I do understand that there are some advantages to character for a field like this but then I'd have to go back and change a bunch of old stuff, yikes!! I've got enough to do (actually too much, but who doesn't?)
Maybe I'll bite the bullet and change it at some point, but then I'd probably start redesigning the whole app and make a lot of work for myself.

Russ

[Stan Mathews]

RE: invert(str(xx)) vs str(invert(xx))

Tom,

I believe Ira had a post once referring to the "characters" appearing in the evaluation box when inverting, combining multiple data types, etc.

I thought I remembered it being referred to as some sort of binary representation, but that doesn't seem right.

[Tom Cone Jr]

RE: invert(str(xx)) vs str(invert(xx))

The hieroglyphics (sp?) come from Alpha's attempt to display characters that have odd decimal ascii equivalents. I think the invert() function returns the mathematic complement of the specified value, though I'd be hard pressed to explain what that means!

[JohnZaleski]

RE: invert(str(xx)) vs str(invert(xx))

Tom,
I think it means nothing.
invert(123.12) = -123.12
invert(123.13) = -123.13
-123.13 comes before -123.12 thus the descending order.

The invert is advertised as nothing but a way to sort values in a descending manner. I think I read something about a5v5 doing more with inverted values in the way of allowing the user to do finds by entering in the actual value rather than the hieroglyphics.
John

[Tom Cone Jr]

RE: invert(str(xx)) vs str(invert(xx))

John,

No fair. You picked the easy one!

From the interactive editor:

?invert(123.56)
= -123.560000

?invert("abc")
= "���"

?invert("Cone, Tom")
= "�����߫��"

?invert({05/02/2001})
= {26/06/-114}

?invert(cdate(date()))
= "��������"


The mathematic complement must be the value which when added to the initial value totals zero. It's easy to understand for numeric values. It's when Alpha Five starts inverting strings that it gets very hard to see...

-- tom

[csda1]

RE: invert(str(xx)) vs str(invert(xx))

Tom,

The invert() function just takes the one's complement of the binary of each ASCII character.

This means that if you had the letter "A" which is 01000001 binary (41 hex or 65 decimal), to get the one's complement, just change the 1's to zeros and zero's to 1's. This yields a 10111110 binary (BE hex or 190). If you wanted to do the equivalent in decimal arithemetic just subtract the Ascii decimal value 65 from 255.

255-65=190

Now take the new value and convert it back to a character in the font by using chr(190).

Regards,

Ira J. Perlow
Computer Systems Design & Associates
[email protected]

[Tom Cone Jr]

RE: invert(str(xx)) vs str(invert(xx))

Thanks Ira. As I indicated above I'd be hard pressed to explain how it works!

[DiFaz]

RE: invert(str(xx)) vs str(invert(xx))

Tom,
I agree!

One of the first "rules" I learned when I first started programming xBase in the mid eighties was:

"If you're not going to do arithmetic with it make it a character field!"

I think that's still good advice!

Ray