title: Adding 2 numbers in NSMutableArray
body: <p>Well, sad to say, but I have 2 questions, which I wish I could've answered myself:</p>
  
  <p>a)  If I have an NSMutableArray of say 5 elements and want to add objects 0 and 1 together, how would I do it?</p>
  
  <p>e.g. </p>
  
  <pre><code>NSMutableArray *a =[[NSMutableArray alloc] initWithObjects:3,7,2, 1,6, nil];
  NSMutableArray *c = [[NSMutableArray alloc] initWithArray:a copyItems:YES];
  
  [c replaceObjectAtIndex:1 withObject:
              ([[c objectAtIndex:0] intValue]+ 
               [[c objectAtIndex:1] intValue])];
  </code></pre>
  
  <p>b) This is the embarrassing part:  how would I create a simple program in Xcode to test this, and try various other iterations?  Is there some pre-made skeleton that has all the stuff you need just to plop down these 3 lines of code?</p>