Math Rules

DS · May 23, 2008

I tried to have this coded properly. It seems to returning all of the
correct answer but one never knows! Could someone please look at my
parentheses to see if they are correct.
Thank you
DS

Select Case Me.TxtCase
Case 1
Me.TxtAnswer = Qty * Price
Case 2
Me.TxtAnswer = (Qty * Price) * Tax
Case 3
Me.TxtAnswer = Qty * Price * (1 + Tax)
Case 4
Me.TxtAnswer = (Qty * Price) * Percent Discount
Case 5
Me.TxtAnswer = (Qty * Price) * (1 - Percent Discount)
Case 6
Me.TxtAnswer = Qty * Dollar Discount
Case 7
Me.TxtAnswer = Qty * (Price - Dollar Discount)
Case 8
Me.TxtAnswer = (Qty * Price) - (Tax * (Qty * Price))
Case 9
Me.TxtAnswer = Tax * (Qty * Price)
Case 10
Me.TxtAnswer = Qty * Price
Case 11
Me.TxtAnswer = (Qty * Price - (Tax * Qty * Price)) * Percent
Discount
Case 12
Me.TxtAnswer = (Qty * Price - (Tax * Qty * Price)) * (1 -
Percent Discount)
Case 13
Me.TxtAnswer = Qty * Dollar Discount
Case 14
Me.TxtAnswer = (Qty * Price - (Tax * Qty * Price)) - Qty *
Dollar Discount
End Select

Ken Snell \(MVP\) · May 23, 2008

How is someone expected to answer whether the parentheses are "correct" when
we have no idea what the desired results / logic are? The "correctness" of
the parentheses depends entirely upon what you are wanting the calculations
to do....and we would just be guessing without more information.

DS · May 23, 2008

Good Point. I just thought there was a Standard Order of things.
DS

John W. Vinson · May 23, 2008

I tried to have this coded properly. It seems to returning all of the
correct answer but one never knows! Could someone please look at my
parentheses to see if they are correct.
Thank you
DS

Select Case Me.TxtCase
Case 1
Me.TxtAnswer = Qty * Price
Case 2
Me.TxtAnswer = (Qty * Price) * Tax
Case 3
Me.TxtAnswer = Qty * Price * (1 + Tax)
Case 4
Me.TxtAnswer = (Qty * Price) * Percent Discount
Case 5
Me.TxtAnswer = (Qty * Price) * (1 - Percent Discount)
Case 6
Me.TxtAnswer = Qty * Dollar Discount
Case 7
Me.TxtAnswer = Qty * (Price - Dollar Discount)
Case 8
Me.TxtAnswer = (Qty * Price) - (Tax * (Qty * Price))
Case 9
Me.TxtAnswer = Tax * (Qty * Price)
Case 10
Me.TxtAnswer = Qty * Price
Case 11
Me.TxtAnswer = (Qty * Price - (Tax * Qty * Price)) * Percent
Discount
Case 12
Me.TxtAnswer = (Qty * Price - (Tax * Qty * Price)) * (1 -
Percent Discount)
Case 13
Me.TxtAnswer = Qty * Dollar Discount
Case 14
Me.TxtAnswer = (Qty * Price - (Tax * Qty * Price)) - Qty *
Dollar Discount
End Select

Ken's point is well taken; nobody here could possibly have any idea what the
logical significance of txtCase might be, or whether your expressions in fact
match your business logic. It's supicious that Tax is used in two different
ways (in cases 2 and 3), and that cases 1 and 10 appear to be identical.

One thing that WILL be a problem is that blanks are meaningful. To VBA, Dollar
and Discount are two independent and unrelated variable names, likewise
Percent Discount. The program will look for variables named "Dollar" and
"Percent" and "Discount" and fail. If these are VBA variables, they cannot
contain blanks; try DollarDiscount and PercentDiscount. If they refer to form
controls, use square brackets: [Dollar Discount], or better, rename the
control to eliminate the blank.

scubadiver · May 23, 2008

You are correct.

http://en.wikipedia.org/wiki/Order_of_operations

but the calculations in your message are still a bit meaningless and you
don't specify what each case is intended to calculate

DS · May 23, 2008

Thanks John, I see the Err of my ways. I appreciate the input about the
blanks. By the way what is the order of operations in math?
Thanks
DS

DS · May 23, 2008

Thanks Scuba Diver, I just asked John for the order of operations, I
couldn't remember the term when I needed it! Thank you for suppling it.
DS

John W. Vinson · May 23, 2008

Thanks John, I see the Err of my ways. I appreciate the input about the
blanks. By the way what is the order of operations in math?

Multiplication and division first, addition and subtraction afterward. I'd be
inclinde to freely use parentheses to make it unambiguous; I'm sure that

A * B + C

will be equivalent to

(A * B) + C

rather than to

A * (B + C)

but it would be clearer and self-documenting if you use the parenthesized
notation.

DS · May 27, 2008

Thanks John, I agree with you. I think the parentheses will work better.
DS

Jan Baird · May 27, 2008