design pattern - common problem and a good solution to it

	iterator
		a consistent way of accessing the elements of 
		any collection
	
	composite
	
		combine primitives into one combined "composite"
			call method on composite -> call method on pieces inside
			can treat the composite the same way as the pieces
			
			provides good nested structure
			
			Your sign is Leo.
			
		
	
	decorator

		add functionality to an existing object
		wraps underlying object
		don't have to modify underlying object
		avoids clutter in underlying objects
		

	observer
	
		polling - asking whether something has happened
		event
	

	strategy
		different variations of an algorithm, implemented as objects
		Comparator
		computer players in poker
			Strategy
				getMove
				placeBet
			setStrategy
			setDifficulty