What does this do?

[twgonder]

I'm working on some binary conversions, and ran across this expression:

(15 And &H1)

Can you tell me what it does and why it evaluates to a 1?
How about what MS documentation applies to this?

Thanks

[June7]

In VBA &H is used to define a color code. Review https://www.accessforums.net/showthread.php?t=88998

Alone, &H1 evaluates to 1 in the immediate window.

Out of context, no way to know what (15 And &H1) is supposed to do. Certainly isn't doing arithmetic or concatenation. And is a logical operator.

Where did you find this?

[twgonder]

In
Where did you find this?

Here is the code it was in. It seems to work, but it's in the category of "it works, but I don't know why":

Public Function DispBinary(ByVal lngVar As Long) As String
    Do While lngVar > 0
        DispBinary = Format(lngVar And &H01, "0") & DispBinary
        lngVar = Int(lngVar / 2)
    Loop
End Function

I messed it up when I copied the code and changed &H01 to &H1, but it still worked.
Whatever it does, it seems quite elegant.

[Welshgasman]

Little obvious really.
It is converting a number to a binary string?

&H1 is hexadecimal 1
&H01 would still be 1
&H00000001 is still 1

? dispbinary(255)
11111111

However Access removes those leading zeroes

I agree though, that it is elegant and now curious as to why you would need it?

[twgonder]

Little obvious really.
It is converting a number to a binary string?

Well yeah, I got that part, the OP was what this bit (pun intended) is doing?

lngVar and &H01

[Welshgasman]

https://en.wikipedia.org/wiki/AND_gate

[twgonder]

@Welshgasman post #6

I'm not sure how that applies, it seems to calculate if the bit is 1 (or 0) for the highest position in the decimal number, which in reality is represented internally to VBA as a binary number, and I'm guessing the format rips off the "-" for a true condition. Wouldn't MS have been kind to just make a CBin() function?

[Welshgasman]

It is ANDING 1 with each bit.
If the bit in the value passed is 1, then you get a 1 as both are 1s, if not 0.
Then you move on to the next bit, by dividing by 2, and so on, until you reach the end of the bits possible.

Yes, a ready made function would be nice (I was wondering how long it was going to take for you to have a moan about MS and Access), so this is really your CBin() function. Easier to type as well?

[twgonder]

@ Welshgasman post #8.

I think I stated the idea in post #7. The question, why is And working with just a bit, and why the highest order bit first. The hex value isn't just one bit nor is the passed in value.

I know, let's make a bunch of variable types for numbers, and then some conversion functions. We won't do hex or binary, because hey, who would ever want to use those on a computer? The users can write a function in VBA so it can execute nice and slow with p-code instead of assembled code. Where is the MS Access documentation to explain this ANDING?

Yes, I know I "whine", but know that it is in direct proportion to the time I spend working around dumb designs, missing or poor documentation, bugs, bugs and more bugs in a product that hasn't progressed much in the last 10 years in either enhancement, Microsoft 365 feel (are you still looking for that zoom feature or VSS compatibility?) or Internet/Wi-Fi capability? Some of the MVP's sites I read are a lot more "whiny" than me when it comes to their experience with MS supporting Access. This isn't anything new on my part, I plow through a lot of old Allen Browne blogs, and most of them start with a WTF Access?!!!

I did read this,
And operator | Microsoft Learn
but I don't understand what they are trying to say about the bitwise comparison. A little better explanation or example would help.

[June7]

A 1 in place of &H1 provides same output.

Exactly what does "ANDING" mean? I have never seen used this way (without an If or IIf). I gather that each side of AND is evaluating to 0 or 1 (nothing to do with True or False). Some experimenting shows that 0 and even numbers return 0 and odd numbers return 1. This expression in place of the Format() also provides same output: IIf(lngVar Mod 2 = 0, 0, 1). And my head stops spinning around the AND mystery.

I have a function that converts decimal to binary but it is longer procedure. I like this new short and sweet version although the other has an additional argument which might make the longer code necessary.

None handle 0 input. Wouldn't you want to return 0?

[isladogs]

Granted there is one MVP who is very negative about MS and Access.
He is no longer posting new content but his negative rants do unfortunately have an impact due to his current status.
His opinions are very different to those of other MVPs and to others posting Access related content on a regular basis.

[Welshgasman]

A 1 in place of &H1 provides same output.

Exactly what does "ANDING" mean? I have never seen used this way (without an If or IIf). I gather that each side of AND is evaluating to 0 or 1 (nothing to do with True or False). Some experimenting shows that 0 and even numbers return 0 and odd numbers return 1. This expression in place of the Format() also provides same output: IIf(lngVar Mod 2 = 0, 0, 1). And my head stops spinning around the AND mystery.

I have a function that converts decimal to binary but it is longer procedure. I like this new short and sweet version although the other has an additional argument which might make the longer code necessary.

None handle 0 input. Wouldn't you want to return 0?

I have never been that comfortable with binary logic TBF, but

? cbin(0)


returns nothing, so either check for len of string or it's value?
Using twgonder's complaint, I renamed it to CBin() :-)

? len(cbin(0))
0

Public Function CBin(ByVal lngVar As Long) As String
    Do While lngVar > 0
        CBin = Format(lngVar And &H1, "0") & CBin
        lngVar = Int(lngVar / 2)
    Loop
End Function

[twgonder]

@IslaDogs post #11: I've read from more than one MVP (around six, most being developers for many years and having been bit several times by MS announcing something new and then in a few years saying "never mind", but I don't think this is the place to name names) that is a bit negative with MS involvement.

To be honest, I have no idea what goes on at MS, just that everything Windows just seems to get more messed up in their effort to emulate Apple. Take Windows 11 Settings vs. the Control Panel. Now how can I keep the computer up at 100% during the incessant updates, without changing all the one-up sleep settings? Windows Explorer...Aggghhhh!

The optimist: The glass is half full
The pessimist: The glass is half empty
The engineer: The glass is too big
Me: Let's find some cleaner water and fill the glass up, please.

[twgonder]

How my functions respond for setting permission flags:

?fConvNumber("1010101010101010101010101010100")
1431655764
?fConvBinary(1431655764)
1010101010101010101010101010100
?fConvBinary(1431655764,1)
True
?fConvBinary(1431655764,31)
False
?fConvBinary(0)
0000000000000000000000000000000
?len(fConvBinary(0))
31
?fConvNumber("1111111111111111111111111111111")
2147483647