Instruction Manual

Throkmorton
Let's go through the code line-by-line and explain what is happening:
//1 By defining the preprocessor macro RW_STD_TYPEDEFS, we enable the set of
Smalltalk-like typedefs. We can then use the typedef SortedCollection instead of
RWBinaryTree, its true identity.
//2 The second #include declares class RWCollectableString, a derived class that multiply
inherits from its base classes RWCString and RWCollectable. RWCollectableString
inherits functionality from RWCString, and "ability to be collected" from class
RWCollectable.
//3 An empty SortedCollection was created at this line.
//4 - //7 Four RWCollectableStrings were created off the heap and inserted into the collection,
in no particular order. See the Class Reference for details on constructors for
RWCollectableStrings. The objects allocated here normally should be deleted before
the end of the program, but we omitted this step to make the example more concise.
//8 A pointer to an RWCollectableString was declared and defined here.
//9 An iterator was constructed from the SortedCollection sc.
//10 The iterator is then used to step through the entire collection, retrieving each value in
order. The function call operator operator()has been overloaded so that the iterator
means "step to the next item and return a pointer to it." All Tools.h++ iterators work
this way. See Stroustrup (1986, Section 7.3.2) for an example and discussion of
iterators, as well as Chapter 10 (Iterators in Collection Classes) of this manual. The
typecast:
str = (RWCollectableString*)sci()
is necessary because the iterator returns an RWCollectable*; that is, a pointer to an
RWCollectable which must then be cast into its actual identity.
//11 Finally, the pointer str is dereferenced and printed. The ability of an
RWCollectableString to be printed is inherited from its base class RWCString.
When run, the program prints out the four collected strings in order; for class
RWCollectableString, this means lexicographical order.