Parse for flag values

[brenaaro]

I have a function that I want to return a long value which is
made up of one or more constant values that I've declared.

I want the calling function to be able to parse that value and
detect which flags were included in the return and take appropriate action.

Can anyone explain to me what conventions I should use in declaring my constants (odd numbers only? prime numbers? etc)
as well as how I should build my return value?

'like this?
    lReturn = myFlag1 Or myFlag2
 
    ' or like this?
    lReturn = myFlag1 And myFlag4 And myFlag5
 
   ' or something else?

I also need to know how to parse the return value to know which flag constants were present. I think that it would be some sort of 'Or' statement, but I'd like to be sure.

Thanks.

[MartinLiss]

What is that you really want to do? Do you just want to know using one return value that one or more values have been set? In that case if you have say 5 values return a string of 5 zeros and ones, with a one indicating that a specific value has been set.

[brenaaro]

I could do something like that, but I'd rather learn the other way.

For example, if you pass multiple flags to the Common Dialog Control

cdg1.Flags = cdlOFNAllowMultiselect Or cdlOFNExplorer

or in a MsgBox as buttons constants

MsgBox "Hello", vbExclamation Or vbYesNoCancel

how does it parse through the value made from the Or statement to determine which flags are included?

[jim mcnamara]

Create constants that are powers of two

2⁰
2¹
2²
....
2³¹

Each power of two sets (or clears) one bit in a long.

[brenaaro]

Ok, that makes sense. What would I use to detect which bits were set/cleared?

[HairyDave]

You can AND you value with the flag - result would be 1 if it exists - 0 if not.

HD

[brenaaro]

Got it, except that (lReturn And myFlag2) equals myFlag2 or 0, not 1 (unless myFlag2 == 1)

Thanks guys.

[HairyDave]

Sorry about that - I wasn't thinking! Of course it gives the flag back.