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*Worthy*
Critical Thinker
Joined: 11 Aug 2003
Posts: 186
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 Posted: Mon Aug 23, 2004 7:45 pm Post subject: |
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6 * 3 / 2 = 9
3 / 2 * 6 = 9
3 * 6 / 2 = 9
Normally, you are right. But here's what will happen in the plotscripting compiler:
6 * 3 / 2 =
18 / 2 = 9
3 / 2 * 6 =
1 * 6 = 6
3 * 6 / 2 =
18 / 2 = 9
In math used outside of OHR, however, you are right. But the early rounding for plotscripting alters the end result. (Or so I think)
~Worthy
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Moogle1
Scourge of the Seas
Halloween 2006 Creativity Winner
Joined: 15 Jul 2004
Posts: 3377
Location: Seattle, WA
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| Posted: Mon Aug 23, 2004 7:48 pm Post subject: |
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It does. A script in SG3 depends on this error.
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TMC
On the Verge of Insanity
Joined: 05 Apr 2003
Posts: 3240
Location: Matakana
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| Posted: Mon Aug 23, 2004 10:14 pm Post subject: |
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| Quote: | | Order of ops doesn't matter when you're only dealing with multiplication and division. |
Other way around. You really only need to worry about this when you are dealing with operations of the same importance of order, such as multiplication and division, because in these cases the order in which the operations are done depends in which order you write them.
Quoting from plotscr.hsd:
| Code: | define operator,begin
20 ^ exponent
30,mod,modulus
30 / divide
30 * multiply
40 -- subtract
40 + add
50 == equal
50 <> notequal
50 << lessthan
50 >> greaterthan
50 <= lessthanorequalto
50 >= greaterthanorequalto
60,xor,xor
60,and,and
60,or,or
70,:=,setvariable
end
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Operations with the smaller number are calculated first, two operations with the same value are calculated in whichever order you write them, where the danger is.
Of interest is 'and' and 'or', which as James pointed out recently, can be used incorrectly in conditional statements.
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Flamer
The last guy on earth...
Joined: 04 Feb 2003
Posts: 725
Location: New Zealand (newly discovered)
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| Posted: Tue Aug 24, 2004 12:41 am Post subject: |
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I don't think it's an error. I mean, Java does the same thing if you're working with integer variables(unless you convert it to double, string or other)
it only accepts integers and truncades the decimals out
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TMC
On the Verge of Insanity
Joined: 05 Apr 2003
Posts: 3240
Location: Matakana
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| Posted: Tue Aug 24, 2004 12:58 am Post subject: |
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Actually, that's true.
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Inferior Minion
Metric Ruler
Joined: 03 Jan 2003
Posts: 741
Location: Santa Barbara, CA
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| Posted: Tue Aug 24, 2004 2:41 am Post subject: |
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But it does matter depending on how the compiler handles integer division.
3 / 2 = 1.5
If the compiler truncates the integer mid calculation then 3 / 2 = 1.
Therefore 3 / 2 * 6 = 6 and 6 * 3 / 2 = 9
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Moogle1
Scourge of the Seas
Halloween 2006 Creativity Winner
Joined: 15 Jul 2004
Posts: 3377
Location: Seattle, WA
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| Posted: Tue Aug 24, 2004 4:37 am Post subject: |
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This is useful in some cases. Say you need to know if a number is divisible by another:
(x / 2 * 2 == x)
is true if x is divisible by 2, false otherwise.
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