Hi there,
I just noticed that the modulo operator % is a little bit weird in XML coding. Usually the modulo operator needs two arguments: the number that is divided and the coefficient. The result should be the remaining of the division. But the SDK reads:
Operator Operation Arguments Example Result
% taking modulo 1 5.3 % 5
what's that? In my understanding, a usual modulo operation is something like:
For the sake of convenience, I'm going to (re)post a reply to a similar question someone once asked at AVSIM. The following is a rather technical reply, but I hope it will serve to illustrate and explain the rather special case of the XML parser's use of the modulus operator:
Hi all,
I understand modulus to a degree, like
123 10 % strips out the 3 and places it on the stack.
what does, say, 2 % do?
The "result" is only obvious whenever you use 10 as a divisor, because it effectively bitshifts the decimal, and the remainder is simply the decimal portion!
With other numbers as a divisor however, the operation is more opaque...
The modulus, or remainder, operator divides number1 by number2 and returns only the remainder as result. The sign of result is the same as the sign of number1. The value of result is between 0 and the absolute value of number2.
For example, in the following expression, A (which is result) equals 5.6.
A = 19 6.7 %
This is equivalent to:
19 / 6.7 = 2.8358208
We throw away the fraction leaving 2 as the result
Now we have:
A = 19 - (6.7 * 2)
Therefore A = 5.6
The above is an example where the result is certainly
not obvious!
The "%" (or "mod") operator in computer languages is simply the remainder. For
example,
17 3 % = 2
because
17 / 3 = 5 rem 2
which in turn means
17 = 3 * 5 + 2
There are some tricky issues when negative numbers are used, but that
shouldn't ordinarily be necessary.
In math (number theory), the term is used a little differently. The
"modulus" is actually not the remainder, but the number you are
dividing by; and "mod" is not an operator, but a label telling "in
what sense two quantities are considered congruent, or equal." For
example, we would say
17 = 11 (mod 3)
(read as "17 is congruent to 11, modulo 3"), meaning that 17 and 11
both leave the SAME remainder when divided by 3. You probably won't
see this usage if you are only reading about programming, but it's
worth being aware of if you look deeper into the math behind it.
The expression a = b (% n) means that n is a divisor of a - b. This
sentence is read, "a is congruent to b modulo n." It is something
like a remainder, because if you subtract a remainder from the
dividend, the divisor will go into the result evenly.
Examples: 100 = 86 (% 7), because 100 - 86 = 14 has 7 as a divisor.
On the other hand, if you divide 100 by 7, the quotient is 14 and
remainder is 2, and 100 = 2 (% 7), too.
Now, back to your original question, what would 123 2 % be?
A = 123 2 %
123 / 2 = 61.5, therefore:
A = 123 - (61 * 2)
A = 1
I hope that this is helpful! It's probably a
lot more than you wanted to know...
ok. thanks again!
I did some experiments with the %-operator. It seems like
