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Original post by westond Im thinking of trying to compress my classes a bit by hashing some of my ID variables.

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Original post by westond I have a set of variables that give an individual game cell a location in the game world... int zone_id int zone_y int zone_x each zone id can be broken down into a description of the area of the world its in as well as being the declaration of the array the cells are held in.

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Original post by westond zone_id=1001 World zone 1 sub zone 1 zone_id=1101 World zone 1 town zone 1 subzone 1 etc... the position is array1001<zone_y,zone_x> what I would like to do is create a cell id that combines all this info ex. zone_id=1001 zone_y=2 zone_x=1 long cell_id=100121 but i need a way of breaking that up when I need zone_id, zone_y, and zone_x. I've looked, but cant find anything that will just read the first 4 digits of cell_id and assign it to zone_id and the 5th digit to zone_y and so on. Im sure there is an easy way of doing this that doesnt involve character arrays and casting. Or am I mistaken?

union CellInfo{    long cell_id;  // 32 bit long integer    struct    {        short zone_id; // 16 bit short integer        char zone_x;   // 8 bit byte        char zone_y;   // 8 bit byte                       // 32 bits total    } cell_info;};

CellInfo myCell;// This line, although assigning a value to cell_id, actually stores stuff// in the same memory which contains zone_id, x, and y...with the first 16// bits being the zone_id, the next 8 being the x, and the last 8 being the y.myCell.cell_id = (id << 16) | (x << 8) | y;// You can then access the fields as follows...long cell_id = myCell.cell_id;short zone_id = myCell.cell_info.zone_id;  // this contains the value of "id" abovechar zone_x = myCell.cell_info.zone_x; // this contains the value of "x" above.

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Original post by jwalsh What do you hope to achieve by doing this? Why not just use a structure or a class? What compells you to try and fit this all into a integer? If you were using bit flags, it would be possible to just pull off the bits, but without writing a little code, there's no way to pull off the characters. What you're doing is essentially trying to treat all this info as a concatenated string. (see long cell_id) Now, if you dont care about how your cell_id appears, you can also use Unions. With a union, you create a byte aligned set of values which all share the same space in memory...for example: By creating a union from the cell_id and the struct, you can now refer to the same space in memory in multiple ways. For example: I'm still not sure WHY you'd want to do this, but here's a possible way to do it. I dont believe unions are in the C++ book, as they are C features, and not strictly C++. In general, you should just store your x, y, and id's in a class. There's no reason that I can think of to hash them all into a single variable. But in either event, I hope this helps. Cheers!

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Original post by jwalsh I'm surprised no one either completed project 2, nor asked the questions necessary for them to do so. At any rate, just wanted to give you cut-off date.