An expression question

[Gerry Abbott]

Probly belongs to a programmers group, but I want to evaluate the expression

If a=b=c=d=e then (if there are all equal)
something
else
something else.

Is there an easy way for this in VB?


Gerry Abbott

[Larry Linson]

Re: An expression question

"Gerry Abbott" wrote
[color=blue]
> If a=b=c=d=e then (if there are all equal)
> something
> else
> something else.
>
> Is there an easy way for this in VB?[/color]

Alas, not as easy as one might hope:

If a=b And b=c And c=d And d=e Then

Because an equal sign in an expression may be evaluated as a logical
operator, you have to be careful. For example:

Dim boolB as Boolean
Dim intA as Integer
Dim intB as Integer

boolB = intA = intB

is a perfectly valid statement. If intA and intB are equal, boolB will be
set to the value of True; if not, boolB will be set to the value False.

Larry Linson
Microsoft Access MVP

[Alan Webb]

Re: An expression question

Gerry,
Assuming a, b, c, d, & e are all variables, then what you wrote will work
fine. A more typical way to write it would be:

If A and B and C and D and E Then
'Do what needs doing
Else
'Do the other thing
End if


"Gerry Abbott" <please@ask.i e> wrote in message
news:x1lGc.3967 $Z14.4998@news. indigo.ie...[color=blue]
> Probly belongs to a programmers group, but I want to evaluate the[/color]
expression[color=blue]
>
> If a=b=c=d=e then (if there are all equal)
> something
> else
> something else.
>
> Is there an easy way for this in VB?
>
>
> Gerry Abbott
>
>
>
>
>[/color]

[CDB]

Re: An expression question

Are you sure, Alan?
If the variables held boolean values, ok, but:

?237 and 237 and 237
237

?237 and 237 and 236
236
Unless A, B or C are zero, A And B And C will always evaluate to not-zero,
or True. Unhelpful.

?237 = 237 = 237
False
A true would be yielded only in a few of the cases where the values were Not
equal.

If the data type is string, then a type mismatch error occurs.

Clive


"Alan Webb" <knogeek@hotmai l.com> wrote in message
news:cGoGc.99$C D4.48075@news.u swest.net...[color=blue]
> Gerry,
> Assuming a, b, c, d, & e are all variables, then what you wrote will work
> fine. A more typical way to write it would be:
>
> If A and B and C and D and E Then
> 'Do what needs doing
> Else
> 'Do the other thing
> End if
>
>
> "Gerry Abbott" <please@ask.i e> wrote in message
> news:x1lGc.3967 $Z14.4998@news. indigo.ie...[color=green]
> > Probly belongs to a programmers group, but I want to evaluate the[/color]
> expression[color=green]
> >
> > If a=b=c=d=e then (if there are all equal)
> > something
> > else
> > something else.
> >
> > Is there an easy way for this in VB?
> >
> >
> > Gerry Abbott
> >
> >
> >
> >
> >[/color]
>
>[/color]

[Michael \(michka\) Kaplan [MS]]

Re: An expression question

"CDB" <alpha@delete.w ave.co.nz> wrote...
[color=blue]
> ?237 and 237 and 237
> 237[/color]

This is expected -- bitmasking works that way....
[color=blue]
> ?237 and 237 and 236
> 236[/color]

Well, &hED and &hEC (the hex forms of the two numbers) sdhare all bytes
except that one -- so this statement, which masks the one byte, will return
exactly that.
[color=blue]
> Unless A, B or C are zero, A And B And C will always evaluate
> to not-zero, or True. Unhelpful.[/color]

Depends on what you are trying to check....
[color=blue]
> ?237 = 237 = 237
> False
> A true would be yielded only in a few of the cases where the values
> were Not equal.[/color]

Instead try:

? 237 = 237 = True
True

and then you will see what is going on. It evalusted your expression as:

(237 = 237) = 237

The first part is True, and thus you get

True = 237

which is of course false.
[color=blue]
> If the data type is string, then a type mismatch error occurs.[/color]

Well, not always (due to VBA evil type conversion):

? "True" = true
True
? "237" = 237
True

Looking at Gerry's original question:
[color=blue][color=green]
> > "Gerry Abbott" <please@ask.i e> wrote in message
> > news:x1lGc.3967 $Z14.4998@news. indigo.ie...[color=darkred]
> > > Probly belongs to a programmers group, but I want to evaluate the[/color]
> > expression[color=darkred]
> > >
> > > If a=b=c=d=e then (if there are all equal)
> > > something
> > > else
> > > something else.
> > >
> > > Is there an easy way for this in VB?[/color][/color][/color]

This will fail, since it will be evaluated as:

If ( ( ( a = b ) = c ) = d ) = e

which will never "work" as intended. Instead try:

If A=B And B=C And C=D and D=E Then

and this will work.


--
MichKa [MS]
NLS Collation/Locale/Keyboard Development
Globalization Infrastructure and Font Technologies
Windows International Division

This posting is provided "AS IS" with
no warranties, and confers no rights.

[Lyle Fairfield]

Re: An expression question

"CDB" <alpha@delete.w ave.co.nz> wrote in
news:ccgn46$bp0 $1@news.wave.co .nz:
[color=blue]
> Are you sure, Alan?
> If the variables held boolean values, ok, but:
>
> ?237 and 237 and 237
> 237
>
> ?237 and 237 and 236
> 236
> Unless A, B or C are zero, A And B And C will always evaluate to
> not-zero, or True. Unhelpful.[/color]

I don't think this is so.

If A, B, and C have no common bits set, as in 1, 2, 4
(00000001,00000 010,00000100), A And B And C will evaulate to zero (False).

I do not think And, of itself, can be used satisfactorily to test equality.
If A, B, and C have a common bit set, as in 2, 6, 10
(00000010,00000 110,00001010), A And B And C will evaulate to two -> non-zero
(True).

An untested air-code method, (but I think it's satisfactory) to test several
whole numbers for equality could be:
CBool((A Or B Or C Or ...) = A)

--
Lyle
--
use iso date format: yyyy-mm-dd
http://www.w3.org/QA/Tips/iso-date
--
The e-mail address isn't, but you could use it to find one.

[David W. Fenton]

Re: An expression question

"Gerry Abbott" <please@ask.i e> wrote in
news:x1lGc.3967 $Z14.4998@news. indigo.ie:
[color=blue]
> Probly belongs to a programmers group, but I want to evaluate the
> expression
>
> If a=b=c=d=e then (if there are all equal)
> something
> else
> something else.
>
> Is there an easy way for this in VB?[/color]

If (a+b+c+d+e)/5 = a Then

That will work reliably only for integers, though, unless you
control the rounding.

You might try:

If a-b+c-d+e = a Then

which would get rid of the floating-point inaccuracies introduced by
division (though there can be floating-point inaccuracies in any
operation).

Of course, what you really want is:

If (b=a) And (c=a) And (d=a) And (e=a) Then

With that, you don't have to worry about floating-point errors at
all.

--
David W. Fenton http://www.bway.net/~dfenton
dfenton at bway dot net http://www.bway.net/~dfassoc

[Alan Webb]

Re: An expression question

CDB,
No, actually. Premature click send on my part.

"CDB" <alpha@delete.w ave.co.nz> wrote in message
news:ccgn46$bp0 $1@news.wave.co .nz...[color=blue]
> Are you sure, Alan?
> If the variables held boolean values, ok, but:
>
> ?237 and 237 and 237
> 237
>
> ?237 and 237 and 236
> 236
> Unless A, B or C are zero, A And B And C will always evaluate to not-zero,
> or True. Unhelpful.
>
> ?237 = 237 = 237
> False
> A true would be yielded only in a few of the cases where the values were[/color]
Not[color=blue]
> equal.
>
> If the data type is string, then a type mismatch error occurs.
>
> Clive
>
>
> "Alan Webb" <knogeek@hotmai l.com> wrote in message
> news:cGoGc.99$C D4.48075@news.u swest.net...[color=green]
> > Gerry,
> > Assuming a, b, c, d, & e are all variables, then what you wrote will[/color][/color]
work[color=blue][color=green]
> > fine. A more typical way to write it would be:
> >
> > If A and B and C and D and E Then
> > 'Do what needs doing
> > Else
> > 'Do the other thing
> > End if
> >
> >
> > "Gerry Abbott" <please@ask.i e> wrote in message
> > news:x1lGc.3967 $Z14.4998@news. indigo.ie...[color=darkred]
> > > Probly belongs to a programmers group, but I want to evaluate the[/color]
> > expression[color=darkred]
> > >
> > > If a=b=c=d=e then (if there are all equal)
> > > something
> > > else
> > > something else.
> > >
> > > Is there an easy way for this in VB?
> > >
> > >
> > > Gerry Abbott
> > >
> > >
> > >
> > >
> > >[/color]
> >
> >[/color]
>
>
>[/color]