Math question: storing 2 numbers in one

  • is there a mathematical way to store 2 numbers (let's say x/y coordinates) as 1 number? perhaps like a seed?

    if my x/y was -3002/1506 there doesn't seem to be a way to store that as 1 number, but is there a way to store a different number that somehow can be extrapolated into these 2?

    You could maybe store them as hex and parse them out.. hex:AE would = 10,14

    I supposed negative numbers would make that even more complicated. Any ideas? it's more of a curiosity...

  • It's more of a programming question that a math one. I guess you could try your luck with bits manipulation, however it's quite limited in its current implementation. See manual's system expression "getbit" and "setbit".

  • Magistross I could program parsing easy enough if it were saved as a string. I'm really asking is there a way to store 2 numbers as a single integer. i.e. do some sort of calculation to the two numbers so that a 3rd number somehow represents them both - one would obviously have to do something to the said 3rd number to "unpack" the other two...

  • I wasn't talking about parsing. getbit() and setbit() are used to set individual bits of a 32-bit integer. One could use them to create a function that take two integers in the 16-bit range and combine them in a single 32-bit integer. If we had bit-shifting operation, that would be much easier to do.

    You could maybe try to use decimal shifting instead :

    -packing

    CombinedInt = FirstInt * 1000000 + SecondInt

    -unpacking

    FirstInt = floor(CombinedInt / 1000000)

    SecondInt = CombinedInt % 1000000

    It would work to combine numbers in the 0-999999 range.

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  • Magistross yeah I've done bit shifting, but I see that as a sort of parsing since you need to elect 16 of the bits to be one number and the remaining 16 to be a different number.

    That (decimal shifting) math is what I was looking for.. cool, thanks! the only problem is negative numbers which presents a real problem.

  • You can offset that too. Add 100000 to the number before storing, and subtract that on restore. As long as no number can be beyond +/- 100000, then it all works out.

  • okay so here's an example:

    X:251 Y:3200

    compress:

    251 * 1,000,000 = 251,000,000 + 3200 = 251,003,200

    unpacking:

    first number:

    251,003,200 / 1,000,000 = 251.0032 (use floor to get 251)

    second number:

    251,003,200 / 1,000,000 = 251.0032 (use floor to get 251)

    251 * 1,000,000 = 251,000,000

    251,003,200 - 251,000,000 = 3200 (or just use mod)

    works perfect!

    for negative numbers:

    X:4 Y:-8

    compress:

    4 + 100,000 = 100,004

    -8 + 100,000 = 99,992

    100,004 * 1,000,000 = 100,004,000,000 + 99,992 = 100,004,099,992

    @blackhornet so far this is a problem right? does this go beyond the highest value? isn't it int32: 2,147,483,647?

  • The numbers Magistross and I picked were arbitrary. What are the maximum values you are expecting to get? Scale the constants based on those.

  • the numbers that I need to use are between -20,000 and 20,000

  • So to offset to a positive, you need only add 20000, pushing the top to 40000. So use 100000 as the multiplier: 2,000,000,000 + 40000 = 2,000,040,000 max.

  • I was having a similar problem and being quite stubborn I was convinced there was a mathematical solution to this and I found one that works for me.

    My problem was storing a bunch of x,y coordinates into a flat list that I could easily reference. I though of the two main ideas posted here and was about to give in to bit shifting when I found something you may be able to put to use. The trick is simple, use a prime number in the equation;

    number = x + prime * y

    hope this helps.

  • akrfranko

    interesting..

    so what is the unpacking formula?

    160, 5001

    compress:

    160 + (3 * 5001) = 15,163

    uncompress:

    ?

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