Chapter Review Questions
=========================

#.  Which is true for a ``Dictionary``: is it mutable or immutable?

#.  Though for some collections, like arrays and lists,
    you can fairly easily replace a ``foreach`` 
    loop with a ``for`` loop, that is not the case if you want to iterate
    through a ``Dictionary``.  How do you go through all the keys in
    a ``Dictionary``?
    
#.  What syntax is there for a ``Dictionary`` that matches that for a ``List``?

#.  How is a ``Dictionary`` like an array?  How is it different?

#.  ``Dictionary`` values are of arbitrary type. What is the restriction on 
    key types?
    
#.  How is a ``HashSet`` different than a ``List``?

#.  What syntax is shared between a ``List`` and a ``HashSet``?
    
#.  Which is more efficient in general:  
    searching for an element of a list or finding the
    value given a key in a dictionary?