You could have a static array set up to hold x units at max. For this approach, you'd have to have some special unit value (like, maybe, hp == 0 and being in a certain state) to indicate which array positions are "empty". Then you'd have a function for creating new units that would search the array for an "empty" spot, and copy the appropriate values in that slot. The drawback of this is, of course, that you only have MAX_UNITS (a constant you define, of course) slots for units, and if the array is filled, no more units can be created. It's fast for both access and creation, requires no special memory considerations like deallocation, but lacks flexibility.
Another idea is, yes, to use linked lists or some other data structure for very flexible unit storage since it can expand and contract at will. If you do this, you'll want to make a linked list class to make item operations and traversal very easy. Performance for both access and creation is linearly dependent upon the number of items in there (linear access is effectively no worse than "normal" arrays, though), but you
will have to make sure you deallocate your nodes, otherwise you'll have memory leaks.
...but don't make your own linked list...
Perhaps the best solution is to use an STL (Standard Template Library, something that comes with every C++ compiler that's essentially part of the language) container such as
list .
list is great because it's guaranteed to have the same performance and behavior characteristics of a doubly-linked list (since it's usually implemented that way). But the class is ready to use and has been tested thoroughly, so it saves you lots of time and effort, not to mention that it does the work of allocating and deallocating the nodes for you. Let me give you an example of how you'd use
list
#include <list>using namespace std; // all STL classes are in the "std" namespace// make a typedef to make unit list declarations easier;// in this case, we're making the typedef the same as a// std::list holding Unit structures.typedef list<Unit> unit_list;unit_list UnitList;void CreateUnit(int hp, int whateverelse){ // create a Unit object and initialize it with whatever was passed Unit new_unit; new_unit.hp = hp; new_unit.whateverelse = whateverelse; // add the unit to the end of the list UnitList.push_back(new_unit);}void KillAllUnits(){ // we traverse STL containers (that don't provide // operator[]) using iterators, which are conceptually // pointers to each node in the list; we start at the // beginning of the list (retrieved by the begin() // function) and keep going until the iterator points to // the imaginary element marking the last + 1 item in the // list (retrieved by the end() function), and we can tell // the iterator to point to the next node in the list using // operator++ for(unit_list::iterator it = UnitList.begin(); it != UnitList.end(); ++it) { // to access the node that the iterator points to, just // dereference the iterator; NOTE: although the // (*ptr).member and ptr->member syntaxes are // functionally equivalent, iterators provide only // operator* (and not also operator->), since not all // items that an iterator points to will actually have // members (*it).hp = 0; (*it).whateverelse = 0; }}
I
strongly urge you to use an STL container (don't wast your time on your own linked list when the STL already made a perfect one for you that requires no babysitting). Not only will you save lots of time in both programming and debugging, but they do everything you'd ever need them to.
Edited by - merlin9x9 on November 27, 2001 3:41:35 PM
Edited by - merlin9x9 on November 27, 2001 3:45:24 PM
) and was thinking of using structs to hold the unit data. Actually, by the time I actually start I''ll probably be using classes but the question is the same. I understand (sort of) how to create an object and access it''s members:
Unit tank;
tank.hp = 55;
I was wondering if it''s possible, however, to somehow declare unit on the fly. For example, what would I do if a player decided to build two tanks? Is it possible to declare a new unit, tank2, when it''s created? I was also thinking about using link-lists, though I don''t know enough about them to know if they''d do the job. Arrays would also work I guess, but it seems like an inefficient way of doing it.
Anyway, lemme know if this is possible; any help is appreciated 
I tried writing a small program to see if I could actually use the technique before I go on. I was thinking I would call the function, create a tank, initialize it, and then display the hp of the tank. I was able to sucessfully display the hp sucessfully when I declared:
