Question

How would you implement a generic stack without using nsmutablearrays?

Answer 1

Something like this I’d think:

@interface Stack {
     id *objects;
     int allocatedSize;
 }

 -(void) push:(id) value;
 -(id) peek;
 -(id) pop;

 @end

 @implementation Stack

  -(void) push:(id) value {
       objects = realloc(objects, ++allocatedSize * sizeof id);
       objects[allocatedSize - 1] = value;
  }

  -(id) pop
  {
        id temp = objects[--allocatedSize];
        objects = realloc(objects, allocatedSize * sizeof id);
        return temp;
  }

  -(id) peek
  {
        return objects[allocatedSize - 1];
  }

 @end

MAJOR NOTICE:
This code is BUGGY at the least. ARC and malloc do NOT work well with each other, so take caution to clear your memory before setting a value. Also, please add error checking, as I wrote this in mobile safari, there wasn’t much time for fancy code checks.